American Journal of Hematology 37:112-119 (1991)
Anaplastic Large Cell Kill Lymphoma Involving Bone Marrow: Marrow Findings and Association With Reactive Hemophagocytosis K.F. Wong, J.K.C. Chan, C.S. Ng, Y.C. Chu, P.W.Y. Lam, and H.L. Yuen institute of Pathology (K.F.W., J.K.C.C., P.W.Y.L.), Medical Unit A (Y.C.C.) and Pediatric Unit A (H.L.Y.), Queen Elizabeth Hospital, and Institute of Pathology, Caritas Medical Center (C.S.N.), Hong Kong
This report describes the bone marrow findings in four patients whose marrow was involved by anaplastic large-cell Ki-1 lymphoma, an uncommon event in this type of lymphoma. In the marrow aspirate smears, the involvement was subtle, and was in the form of isolated large cells with irregular nuclear configuration, coarse chromatin, prominent nucleoli, and basophilic cytoplasm which might be vacuolated. One case showed paradoxically massive involvement in the trephine biopsy taken from the same site as the marrow aspirate. Reactivehistiocytic proliferation with hemophagocytosiswas also present. Since marrow aspirate or biopsy may be the first pathologic specimen examined in patients having anaplastic large-cell Ki-1 lymphoma, it is important to be able to recognize the small population of neoplastic cells, which should lead to prompt treatment or further investigations as deemed necessary. Key words: anaplastic large cell lymphoma, marrow involvement, hemophagocytic syndrome
INTRODUCTION
Anaplastic large cell Ki-1 lymphoma, a recently characterized type of malignant lymphoma [ 1-51, rarely involves the bone marrow. We report the hematologic and bone marrow findings of four such cases, which are identified from 24 consecutive cases of anaplastic largecell Ki-1 lymphoma (16 cases of which have previously been reported [ 11). The pattern of involvement is subtle, and all four cases are associated with the development of reactive hemophagocytosis 16-91. We also emphasize the features that are helpful in identifying the lymphoma cells.
3 and 4) by using a panel of monoclonal antibodies reactive with leukocytes in paraffin sections including MT1 (CD43, T-cell), UCHLl (CD45R0, T-cell), L26 (CD20, B-cell), 4KB5 (CD45R, B-cell), Mac387 (macrophage), KP 1 (CD68, macrophage), and Ber-H2 (CD30, Ki-1 antigen). The antibodies were obtained from Dakopatts, Denmark, except for MT1 (Biotest, Germany) [ 1,101. In addition, fresh tissue of lymph node was available for immunophenotyping in case 3 by using a comprehensive panel of monoclonal antibodies previously described [I].
CASE REPORTS Case 1 MATERIALS AND METHODS A 76-year-old man presented in October 1983 with The clinical records, peripheral blood smears, Ro- fever and weight loss. Examination revealed cervical manowsky-stained marrow aspirate smears, and biopsy lymphadenopathy and hepatosplenomegaly. The blood materials of the four cases were reviewed. The histologic counts were: hemoglobin 9 g/dl, white cells 4.6 X 109/1, features of the lymph nodes from cases 1 and 2 have been reported as cases 9 and 10 in a series of anaplastic large-cell Ki-1 lymphoma [ 11. Immunohistochemical Received for publication June 6, 1990; accepted December 20, 1990. studies were performed on paraffin sections of the lymph Address reprint requests to Dr. K.F. Wong, Institute of Pathology, node biopsies (all four cases) and marrow biopsies (cases Queen Elizabeth Hospital, Wylie Road, Kowloon, Hong Kong.
0 1991 Wiley-Liss, Inc.
Case Report: Ki-Lymphoma in Marrow
113
splenomegaly . The blood counts were: hemoglobin 8.2 g/dl, white cells 8.8 X lo9& and platelets 123 X 109/l. The platelet count gradually dropped to 30 X 109/1before initiation of chemotherapy. Computerized tomography of the abdomen showed multiple enlarged paraaortic lymph nodes. Biopsy of the left cervical lymph node yielded a diagnosis of anaplastic large-cell Ki- 1 lymphoma. In the Case 2 bone marrow aspirate, very rare large lymphoid cells and A 19-year-old male presented in June 1984 with a some reactive histiocytes were present among normal 2-week history of swinging fever and sore throat. Exam- hemopoietic cells. However, the trephine biopsy taken ination revealed generalized lymphadenopathy with no from the same site showed massive involvement by hepatosplenomegaly . The blood counts were: hemoglo- lymphoma. She was treated with various chemotherapeubin 13.9 gidl, white cells 3.4 X lo9& and platelets tic regimes including CHOP, MACOP-B, and a regime 322 X 109/l. A diagnosis of “malignant histiocytosis” used for childhood acute lymphoblastic leukemia, but was made from bone marrow aspirate and lymph node each resulted in only transient response with rapid biopsy. He was treated with chemotherapy including recurrence of the organomegaly. The course was comcyclophosphamide, adriamycin, vincristine, and pred- plicated by the development of hemorrhagic infarct of the nisone (CHOP), which resulted in complete remission. brainstem, hyperglycemia, and sepsis. She was alive The blood counts after treatment were: hemoglobin 15.3 with disease as at November 1990. gidl, white cells 6.8 X 109/1, and platelets 292 X 109/l. He has remained disease-free at 6 years. The diagnosis Pathology The lymph nodes showed incomplete effacement of the was recently revised to anaplastic large-cell Ki- 1 lymarchitecture and sinusoidal infiltration by large lymphoma after further immunohistochemical studies. phoma cells which possessed reniform nuclei, prominent Case 3 nucleoli, and abundant amphophilic cytoplasm. The A 30-year-old female presented in September 1989 cytological features were those of type I1 anaplastic with swinging fever and right groin mass. Examination large-cell lymphoma as we previously defined it [ 11. revealed left cervical and right inguinal lymphadenopa- Fibrosis was marked in cases 2 and 3. Intermingled with thy, but no hepatosplenomegaly. Biopsy of the left the large lymphoma cells were histiocytes with indented cervical lymph node yielded a diagnosis of anaplastic nuclei, fine chromatin, and indistinct nucleoli; some large-cell Ki- 1 lymphoma. The blood counts were: showed erythrophagocytosis. The lymphoma cells were hemoglobin 11.7 /dl, white cells 13.2 X 109/1, and immunoreactive with the CD30 antibody Ki-1 or Ber-H2. platelets 375 X 10 /1. The bone marrow aspirate per- Case 1 exhibited B-lineage markers, and case 2 and 4 formed at diagnosis was reported as “normal,” but on T-lineage markers. Case 3 failed to express any B-lineage review, a few isolated lymphoma cells were present. or T-lineage antigens even on application of a broad panel Despite administration of combination chemotherapy of monoclonal antibodies on frozen sections, and was which included methotrexate, adriamycin, cyclophos- therefore considered “non-B non-T.” The bland-looking phamide, vincristine, prednisone, and bleomycin (MA- histiocytes, including the erythrophagocytic ones, were COP-B), there was progressive enlargement of the lymph negative for Ki- 1, T-markers, and B-markers, and nodes. Three months later, she developed anemia and stained with the macrophage markers Mac387 and KPl . The peripheral blood smears showed normochromic leukopenia: hemoglobin 9.8 g/dl, white cells 2.9 X lo9/ 1, and platelets 201 X 109/l. Circulating lymphoma cells normocytic red cells with no poikilocytosis. The differwere found in the peripheral blood smears, and marrow ential counts were normal. Rare circulating lymphoma involvement by lymphoma was confirmed. High-dose cells, which accounted for 2-376 of the total white cells, cytosine arabinoside and mitoxantrone were then given. were found in case 3 three months after presentation (Fig. There was initial partial response with shrinkage of the 1). The bone marrow aspirate smears revealed hypercellymph nodes and improvement of the leukopenia (white cells 3.9 x 109/l).However, 1 month later, she devel- lularity, active hemopoiesis, and adequate megakaryooped progressive organomegaly and disseminated intra- cytes. Increased histiocytes were found, with many showing phagocytosed hemopoietic cells; these histiovascular coagulopathy, and died in March 1990. cytes were mature-looking with inconspicuous nucleoli Case 4 and copious pale grey-blue cytoplasm. The reactive A 16-year-old girl presented in June 1990 with a hemophagocytic component was not evident in the initial I-week history of swinging fever and low back pain. marrow specimen from case 3, and was not very promExamination revealed left cervical lymphadenopathy and inent in case 4. Interspersed among the hemopoietic cells and platelets 27 X 10y/l. A diagnosis of “malignant histiocytosis” was made from bone marrow aspirate and lymph node biopsy. The diagnosis was subsequently revised to anaplastic large-cell Ki- 1 lymphoma. The patient refused any treatment and died of the disease after 1 month.
8
114
Case Report: Wong et al.
were small numbers of large lymphoma cells that occurred singly, or rarely in small groups. These lymphoma cells accounted for 1% to 5% of the marrow nucleated cells (Fig. 2). They were variable in size, ranging from being bigger than a promyelocyte to approximating that of a megakaryocyte. They had irregular nuclear folds, open chromatin, multiple prominent nucleoli, and abundant basophilic agranular cytoplasm. Some cells were finely vacuolated particularly in the peripheral rim of the cytoplasm, and some had cytoplasmic blebs. Many exhibited a pale paranuclear Golgi. Rare tumour cells of case 2 exhibited erythrophagocytosis as well (Fig. 3). Marrow biopsies were available for review in cases 3 and 4. The large neoplastic cells were difficult to identify in case 3, and immunostaining with Ber-H2 highlighted this minor population. In case 4, the marrow biopsy obtained from the same site as the aspirate paradoxically showed extensive infiltration by lymphoma cells contrasting with the subtle infiltration in the aspirate smears (Fig. 4). DISCUSSION Anaplastic large-cell Ki- 1 lymphoma rarely involves the bone marrow (Table I), with the reported frequency ranging from 0% to 30.4%. The overall frequency is probably in the region of 10-15%, similar to that reported for diffuse large-cell lymphoma or diffuse large-cell immunoblastic lymphoma [24]. There has been little description in the literature on the marrow aspirate findings of anaplastic large-cell Ki-1 lymphoma [ 1,181 though the marrow biopsy findings have been briefly alluded to [ 1,3,23]. Like the previous reports, the present four cases also demonstrate the subtlety of the lymphomatous infiltrate in the form of isolated cells interspersed among hemopoietic cells. Furthermore, in the series of Delsol et al. [3], two of the five cases were detected to show marrow involvement only by immunostaining for the Ki-1 antigen. Distinction of these large lymphoma cells from megakaryoblasts [25,26] may be at times difficult. The distinguishing features of these large lymphoma cells include the more irregularly folded nuclei, more open but coarse chromatin, multiple prominent nucleoli, more abundant cytoplasm, frequent presence of a pale paranuclear hof, and frequent occurrence of vacuoles. Taken together, these findings are characteristic of anaplastic large-cell lymphoma. Distinction of these large lymphoma cells from histiocytes can also be difficult, but their nuclei and nucleoli are much bigger, and the cytoplasm is much more basophilic. In contrast to most studies, the recent study by Chott et al. 2231 described a high incidence of marrow involvement by Ki-I-positive large-cell lymphoma (seven out of 23 cases). In their report, marrow involvement was limited to those cases exhibiting the group B morphology
(similar to what we delineated as type I morphology [l]) and those occurring in patients over the age of 40 years, and the involvement was sometimes massive. However, in the present series, all the cases with marrow involvement showed type I1 (basophilic cell) morphology. Furthermore, three of the four patients were under 40 years of age. Thus, the morphology of the lymphoma cells cannot be used to predict dissemination of disease, nor is age itself a reliable indicator. Another interesting feature of these four cases is the increase of hemophagocytic histiocytes in the marrow. The finding of atypical mononuclear cells (lymphoma cells) and hemophagocytic cells conforms to the original description of “malignant histiocytosis” [9,27]. However, the cytologically atypical cells in our cases express the Ki-1 antigen and B- or T-lineage markers (except one case) but not histiocytic markers, which does not provide support that they represent histiocytic cells. Neither is erythrophagocytosis by the neoplastic cells (as observed in case 2) pathognomonic of histiocytes, as this phenomenon has been observed in some T-cell lymphomas and in other neoplasms [28,29]. On the other hand, the intermingled bland-looking histiocytes (including the hemophagocytic ones) in the marrow or the lymph node exhibit a histiocytic phenotype (Mac387 and KPl positive, and Ki-1 negative). We interpret these histiocytes as being a reactive component rather than a differentiated component of the neoplastic process, because they are immunophenotypically distinct from the neoplastic cells, they lack cytological atypia, and identical histiocytes are found in reactive hemophagocytic syndrome in the absence of lymphoma. This contention, however, remains to be proven when suitable clonal markers become available. In these examples of malignant lymphoma complicated by reactive hemophagocytosis [6,7,19,30], it is likely that the histiocytic proliferation results from lymphokines secreted by the lymphoma cells, which are probably activated as evidenced by the expression of Ki-1 antigen and other activation markers [ I]. Furthermore, most cases previously reported as “malignant histiocytosis” have now been reinterpreted as examples of malignant lymphoma, mostly of T-cell lineage and with a high frequency of Ki-1 positivity [3,19,30-321. The importance of recognizing the subtle pattern of marrow infiltration in anaplastic large cell Ki-1 lymphoma is three-fold. First, marrow involvement signifies stage IV disease and calls for systemic chemotherapy instead of locoregional therapy which might have been considered as an alternative. As illustrated by case 4, marrow biopsy should always be performed in addition to aspirate. Immunostaining with Ber-H2 (CD30) on paraffin sections of the marrow clot or biopsy is very helpful for picking out the neoplastic cells though the staining may be patchy; plasma cells are also stained but they can be readily recognized as such. We have attempted
Case Report: Ki-Lymphoma in Marrow
Fig. 1. Circulating lymphoma cells in case 3. Note the irregular nuclei, prominent nucleoli, and cytoplasmic vacuoles. Romanowsky. x600.
115
Fig. 2. Medium-power view illustrating the subtlety of the infiltrate. An isolated lymphoma cell (double arrow) is found among the hemopoietic cells. Reactive histiocytes (arrows) with hemophagocytosis are also shown. Romanowsky.
x300.
116
Case Report: Wong et al.
Fig. 3. A-F: Composite figure showing lymphoma cells (A-E) and reactive histiocytes (F). A-C: Lymphoma cells with lobulated nuclei, prominent nucleoli, coarse chromatin, dark-staining cytoplasm, and cytoplasmic blebs. D: Lymphoma cell with a nuclear hole (“doughnut”). Note the
cytoplasmic vacuoles and blebs. E: Lymphoma cells showing erythrophagocytosis. F: Erythrophagocytic histiocytes for comparison. They have smaller nuclei, less coarse chromatin, and indistinct nucleoli. Romanowsky. x 1,250.
Case Report: Ki-Lymphoma in Marrow
Fig. 4. Case 4. A: In the marrow smear, only very rare lymphoma cells (arrows) are identified. Romanowsky. x300. B: Marrow biopsy taken from same site, however, shows extensive infiltration by lymphoma cells. Hematoxylin-eosin. x 400.
117
118
Case Report: Wong et al.
TABLE 1. Frequency of Marrow Involvement in Ki-1 Large-Cell Lymphoma
Report (Ref. No.)”
Frequency
Stein et al., 1985 [51 Kadin et al., 1986 [41 Agnarsson and Kadin, 1988 [2] Delsol et al., 1988 [3] Schnitzer et al., 1988 [ I 11 Tourneau et al., 1988 [12] Weiss et al., 1988 [131 Bejaards et al., 1989 [I41 Chan et al., 1989 (updated in this report) [ I ] Kaneko et al., 1989 [IS] Kaudewitz et al., 1989 [ 161 Tashiro et al., 1989 [17] Kinney et al., 1990 1181 Mason et al., 1990 (191 Rosso et al., 1990 [20] Burns and Dardick, 1990 [21] Bitter et al., 1990 [22] Chott et al., 1990 [23]
Not stated 016 2128 5134 013 014 Not stated 0110 (cutaneous lymphoma) 4124 013 01 15 (cutaneous lymphoma)
2112 2112 1112 015 014 019 7123
4
5
6
7
8. 9.
10.
aOnly those series with more than 2 cases are tabulated. 11.
12.
immunostaining with Ber-H2 on stored methanol-fixed marrow smears by using the alkaline phosphatase antialkaline phosphatase technique, but the results were unsatisfactory. If freshly prepared smears are available, application of the Ki-1 antibody would probably be helpful in identifying the neoplastic population. Second, the few large atypical (lymphoma) cells in the marrow aspirate may represent the first clue to the neoplastic nature of the whole disease process, which should lead to prompt treatment or further investigations as required. Since the patients not uncommonly present with cytopenia, it is likely that bone marrow aspirate or biopsy may represent the first pathologic specimen examined. Third, in patients presenting with hemophagocytic syndrome, the marrow smears and biopsies should be scrutinized for lymphoma cells which may be “hiding” among the hemopoietic cells. Lymphoma would require treatment with cytotoxic drugs, whereas they are contraindicated in infection-associated hemophagocytic syndrome [7,9,33].
13
14
15
16
17
18
19
REFERENCES I . Chan JKC, Ng CS. Hui PK, Leung TW, Lo ESF, Lau WH, McGuire LJ: Anaplastic large cell Ki-l lymphoma, delineation of two morphological types. Histopathology 15: 1 1-34, 1989. 2. Agnarsson BA. Kadin ME: Ki-1 positive large cell lymphoma, a inorphologic and immunologic study of 19 cases. Am J Surg Pathol 121264274. 1988. 3. Delsol G, Saati TA. Gatter KC, Gerdes J , Schwarting R, Caveriviere P, Rigal-Huguet F, Robert A, Stein H , Mason DY: Co-expression of epithelial membrane antigen (EMA), Ki- 1 and interleukin-2 receptor
20
21
by anaplastic large cell lymphomas, diagnostic value in so-called malignant histiocytosis. Am J Pathol 13059-70, 1988. Kadin ME, Sako D, Berliner N, Franklin W, Woda B, Borowitz M, Ireland K, Schweid A, Herzog P, Lange B, Dorfman R: Childhood Ki-l lymphoma presenting with skin lesions and peripheral lymphadenopathy. Blood 68:1042-1049, 1986. Stein H, Mason DY, Gerdes J, O’Connor N, Wainscoat J, Pallesen G, Gatter K, Falini B, Delsol G, Lemke H, Schwarting R, Lennert K: The expression of the Hodgkin’s disease associated antigen Ki- I in reactive and neoplastic lymphoid tissue: Evidence that Reed-Stemberg cells and histiocytic malignancies are derived from activated lymphoid cells. Blood 66348-858, 1985. Jaffe ES, Costa J , Fauci AS, Cossman J, Tsokos M: Malignant lymphoma and erythrophagocytosis simulating malignant histiocytosis. Am J Med 75:741-749, 1983. Chan JKC, Ng CS, Law CK, Ng WF, Wong KF: Reactive hemophagocytic syndrome, a study of 7 fatal cases. Pathology 19:43-50, 1987. Ng CS, Chan JKC, Cheng PNM, Szeto SC: Nasal T cell lymphoma associated with hemophagocytic syndrome. Cancer 58:67-7 1, 1986. Reiner AP, Spivak JL: Hemophagocytic histiocytosis, a report of 23 new patients and a review of the literature. Medicine 67:369-388, 1988. Chan JKC, Ng CS, Hui PK: A simple guide to the terminology and application of leukocyte monoclonal antibodies (Review). Histopathology 12:441-460, 1988. Schnitzer B, Roth MS, Hyder DM, Ginsburg D: Ki-l lymphoma in children. Cancer 61:1213-1221, 1988. Toumeau AL, Andouin J, Diebold J: Ultrastructural study of four cases of Ki-l positive large cell anaplastic malignant lymphoma. Virchows Arch [A] 413:215-222, 1988. Weiss LM, Picker LJ, Copenhaver CM, Wamke RA, Sklar J: Large cell hematolymphoid neoplasms of uncertain lineage. Hum Pathol 191967-973, 1988. Bejaards RC, Meijer CJLM, Scheffer E: Prognostic significance of CD30 (Ki- liBer-H2) expression in primary cutaneous large-cell lymphomas of T-cell origin, a clinicopathologic and immunohistochemical study in 20 patients. Am J Pathol 135:1169-1178, 1989. Kaneko Y, Frizzera G, Edamura S, Maseki N, Sakurai M, Komada Y, Sakurai M, Tanaka H, Sasaki M, Suchi T, Kikuta A, Wasaka H, Hojo H, Mizutani S: A novel translocation, t(2;5)(p23;q35), in childhood phagocytic large T-cell lymphoma mimicking malignant histiocytosis. Blood 732306-813, 1989. Kaudewitz P, Stein H, Dallenbach F, Eckert F, Bieber K, Burg G, Braun-Falco 0: Primary and secondary cutaneous Ki-l + (CD30t) anaplastic large cell lymphomas, morphologic, immunohistologic and clinical characteristics. Am J Pathol 135:359-367, 1989. Tdshiro K, Kikuchi M, Tokeshita M, Yoshida T, Ohishima K: Clinicopathological study of Ki- 1 positive lymphoma. Pathol Res Pract 185:461467, 1989. Kinney MC, Greer JP, Macon WR, Collins RD: Peripheral blood and marrow involvement in Ki-1 anaplastic large cell malignant lymphoma (Abstract). Lab Invest 62:52A2,1990. Mason DY, Bastard C, Rimokh R, Dastugue N, Huret J-L, Kristoffersson U , Magaud J-P, Nezelof C, Tilly H, Vannier J-P, Hemet J, Wamke R: CD30-positive large cell lymphomas (‘Ki-1 lymphoma’) are associated with a chromosomal translocation involving 5q35. Br J Haematol 74:161-168, 1990. Rosso R, Paulli M, Margrini U, Kindl S, Boveri E, Volpato G, Poggi S , Baglioni P, Pileri S: Anaplastic large cell lymphoma, CD30IKi-1 positive, expressing the CD WLeu-MI antigen-Immunohistochemical and morphological relationships to Hodgkin’s disease. Virchows Arch [A] 416:229-235, 1990. Bums FB, Dardick I: Ki- 1-positive non-Hodgkin’s lymphomas-an immunophenotypic, ultrastructural, and morphometric study. Am J Clin Pathol 93:327-332, 1990.
Case Report: Ki-Lymphoma in Marrow 22. Bitter MA, Franklin WA, Larson RA, McKeithan TW, Rubin CM, Le Beau MM, Stephens JK, Vardiman JW: Morphology in Ki-l(CD3O)positive non-Hodgkin’s lymphoma is correlated with clinical features and the presence of a unique chromosomal abnormality, t(2;5)(p23;q35). Am J Surg Pathol 14:305-316, 1990. 23. Chott A, Kaserer K, Augustin I, Vesely M, Heinz R, Oehlinger W, Hanak H, Radaszkiewicz T: Ki-1 positive large cell lymphoma, a clinicopathologic study of 41 cases. Am J Surg Pathol 14:439-448, 1990. 24. Rosenberg SA, Berard CW, Brown BW, Burke J , Dorfman RF, Glatstein E, Hoppe RT, Simon R: National Cancer Institute sponsored study of classification of non-Hodgkin’s lymphomas. Summary and description of a working formulation for clinical use. Cancer 49:21122135, 1982. 25. Williams N, Levine RF: The origin, development and regulation of rnegakaryocytes. Br J Haematol 52: 173-180, 1982. 26. Zucker-Franklin D: Megakaryocytes and platelets. In Zucker-Franklin, Greaves MF, Grossi CE, Marmont AM (eds): “Atlas of Blood Cells-Function and Pathology.” Philadelphia: Lea & Febiger, 1988, pp 619-693. 27. Wamke RA, Kim H, Dorfman RF: Malignant histiocytosis (histiocytic medullary reticulosis), clinicopathologic study of 29 cases. Cancer 35:2 15-230. 1975.
119
28. Kadin ME, Kamoun M, Lamberg J: Erythrophagocytic Ty lymphoma, a clinicopathologic entity resembling malignant histiocytosis. N Engl J Med 304:648-653, 1981. 29. Falini B, Bucciarelli E, Grignani F, Martelli MF: Erythrophagocytosis by undifferentiated lung carcinoma cells. Cancer 46: I 14C1145, 1980. 30. Falini B, Pileri S, De Solas I, Martelli MF, Mason DY, Delsol G, Gatter KC, Fagioli M: Peripheral T-cell lymphoma associated with hemophagocytic syndrome. Blood 75:434444, 1990. 31, Wilson MS, Weiss LM, Gatter KC, Mason DY, Dorfman RF, Warnke RA: Malignant histiocytosis, a reassessment of cases previously reported in 1975 based upon paraffin section immunophenotyping studies. Cancer 66:53&536, 1990. 32. Cattoretti G , Villa A, Vezzoni P, Giardini R, Lombardi L, Rilke F: Malignant histiocytosis, a phenotypic and genotypic investigation. Am J Pathol 136:1009-1019, 1990. 33. Risdall RJ, McKenna RW, Nesbit ME, Krivit W, Balfour HH, Simmons RL, Brunning RD: Virus-associated hemophagocytic syndrome, a benign histiocytic proliferation distinct from malignant histiocytosis. Cancer 44:993-1002, 1979.
Anaplastic Large Cell Kill Lymphoma Involving Bone Marrow: Marrow Findings and Association With Reactive Hemophagocytosis K.F. Wong, J.K.C. Chan, C.S. Ng, Y.C. Chu, P.W.Y. Lam, and H.L. Yuen institute of Pathology (K.F.W., J.K.C.C., P.W.Y.L.), Medical Unit A (Y.C.C.) and Pediatric Unit A (H.L.Y.), Queen Elizabeth Hospital, and Institute of Pathology, Caritas Medical Center (C.S.N.), Hong Kong
This report describes the bone marrow findings in four patients whose marrow was involved by anaplastic large-cell Ki-1 lymphoma, an uncommon event in this type of lymphoma. In the marrow aspirate smears, the involvement was subtle, and was in the form of isolated large cells with irregular nuclear configuration, coarse chromatin, prominent nucleoli, and basophilic cytoplasm which might be vacuolated. One case showed paradoxically massive involvement in the trephine biopsy taken from the same site as the marrow aspirate. Reactivehistiocytic proliferation with hemophagocytosiswas also present. Since marrow aspirate or biopsy may be the first pathologic specimen examined in patients having anaplastic large-cell Ki-1 lymphoma, it is important to be able to recognize the small population of neoplastic cells, which should lead to prompt treatment or further investigations as deemed necessary. Key words: anaplastic large cell lymphoma, marrow involvement, hemophagocytic syndrome
INTRODUCTION
Anaplastic large cell Ki-1 lymphoma, a recently characterized type of malignant lymphoma [ 1-51, rarely involves the bone marrow. We report the hematologic and bone marrow findings of four such cases, which are identified from 24 consecutive cases of anaplastic largecell Ki-1 lymphoma (16 cases of which have previously been reported [ 11). The pattern of involvement is subtle, and all four cases are associated with the development of reactive hemophagocytosis 16-91. We also emphasize the features that are helpful in identifying the lymphoma cells.
3 and 4) by using a panel of monoclonal antibodies reactive with leukocytes in paraffin sections including MT1 (CD43, T-cell), UCHLl (CD45R0, T-cell), L26 (CD20, B-cell), 4KB5 (CD45R, B-cell), Mac387 (macrophage), KP 1 (CD68, macrophage), and Ber-H2 (CD30, Ki-1 antigen). The antibodies were obtained from Dakopatts, Denmark, except for MT1 (Biotest, Germany) [ 1,101. In addition, fresh tissue of lymph node was available for immunophenotyping in case 3 by using a comprehensive panel of monoclonal antibodies previously described [I].
CASE REPORTS Case 1 MATERIALS AND METHODS A 76-year-old man presented in October 1983 with The clinical records, peripheral blood smears, Ro- fever and weight loss. Examination revealed cervical manowsky-stained marrow aspirate smears, and biopsy lymphadenopathy and hepatosplenomegaly. The blood materials of the four cases were reviewed. The histologic counts were: hemoglobin 9 g/dl, white cells 4.6 X 109/1, features of the lymph nodes from cases 1 and 2 have been reported as cases 9 and 10 in a series of anaplastic large-cell Ki-1 lymphoma [ 11. Immunohistochemical Received for publication June 6, 1990; accepted December 20, 1990. studies were performed on paraffin sections of the lymph Address reprint requests to Dr. K.F. Wong, Institute of Pathology, node biopsies (all four cases) and marrow biopsies (cases Queen Elizabeth Hospital, Wylie Road, Kowloon, Hong Kong.
0 1991 Wiley-Liss, Inc.
Case Report: Ki-Lymphoma in Marrow
113
splenomegaly . The blood counts were: hemoglobin 8.2 g/dl, white cells 8.8 X lo9& and platelets 123 X 109/l. The platelet count gradually dropped to 30 X 109/1before initiation of chemotherapy. Computerized tomography of the abdomen showed multiple enlarged paraaortic lymph nodes. Biopsy of the left cervical lymph node yielded a diagnosis of anaplastic large-cell Ki- 1 lymphoma. In the Case 2 bone marrow aspirate, very rare large lymphoid cells and A 19-year-old male presented in June 1984 with a some reactive histiocytes were present among normal 2-week history of swinging fever and sore throat. Exam- hemopoietic cells. However, the trephine biopsy taken ination revealed generalized lymphadenopathy with no from the same site showed massive involvement by hepatosplenomegaly . The blood counts were: hemoglo- lymphoma. She was treated with various chemotherapeubin 13.9 gidl, white cells 3.4 X lo9& and platelets tic regimes including CHOP, MACOP-B, and a regime 322 X 109/l. A diagnosis of “malignant histiocytosis” used for childhood acute lymphoblastic leukemia, but was made from bone marrow aspirate and lymph node each resulted in only transient response with rapid biopsy. He was treated with chemotherapy including recurrence of the organomegaly. The course was comcyclophosphamide, adriamycin, vincristine, and pred- plicated by the development of hemorrhagic infarct of the nisone (CHOP), which resulted in complete remission. brainstem, hyperglycemia, and sepsis. She was alive The blood counts after treatment were: hemoglobin 15.3 with disease as at November 1990. gidl, white cells 6.8 X 109/1, and platelets 292 X 109/l. He has remained disease-free at 6 years. The diagnosis Pathology The lymph nodes showed incomplete effacement of the was recently revised to anaplastic large-cell Ki- 1 lymarchitecture and sinusoidal infiltration by large lymphoma after further immunohistochemical studies. phoma cells which possessed reniform nuclei, prominent Case 3 nucleoli, and abundant amphophilic cytoplasm. The A 30-year-old female presented in September 1989 cytological features were those of type I1 anaplastic with swinging fever and right groin mass. Examination large-cell lymphoma as we previously defined it [ 11. revealed left cervical and right inguinal lymphadenopa- Fibrosis was marked in cases 2 and 3. Intermingled with thy, but no hepatosplenomegaly. Biopsy of the left the large lymphoma cells were histiocytes with indented cervical lymph node yielded a diagnosis of anaplastic nuclei, fine chromatin, and indistinct nucleoli; some large-cell Ki- 1 lymphoma. The blood counts were: showed erythrophagocytosis. The lymphoma cells were hemoglobin 11.7 /dl, white cells 13.2 X 109/1, and immunoreactive with the CD30 antibody Ki-1 or Ber-H2. platelets 375 X 10 /1. The bone marrow aspirate per- Case 1 exhibited B-lineage markers, and case 2 and 4 formed at diagnosis was reported as “normal,” but on T-lineage markers. Case 3 failed to express any B-lineage review, a few isolated lymphoma cells were present. or T-lineage antigens even on application of a broad panel Despite administration of combination chemotherapy of monoclonal antibodies on frozen sections, and was which included methotrexate, adriamycin, cyclophos- therefore considered “non-B non-T.” The bland-looking phamide, vincristine, prednisone, and bleomycin (MA- histiocytes, including the erythrophagocytic ones, were COP-B), there was progressive enlargement of the lymph negative for Ki- 1, T-markers, and B-markers, and nodes. Three months later, she developed anemia and stained with the macrophage markers Mac387 and KPl . The peripheral blood smears showed normochromic leukopenia: hemoglobin 9.8 g/dl, white cells 2.9 X lo9/ 1, and platelets 201 X 109/l. Circulating lymphoma cells normocytic red cells with no poikilocytosis. The differwere found in the peripheral blood smears, and marrow ential counts were normal. Rare circulating lymphoma involvement by lymphoma was confirmed. High-dose cells, which accounted for 2-376 of the total white cells, cytosine arabinoside and mitoxantrone were then given. were found in case 3 three months after presentation (Fig. There was initial partial response with shrinkage of the 1). The bone marrow aspirate smears revealed hypercellymph nodes and improvement of the leukopenia (white cells 3.9 x 109/l).However, 1 month later, she devel- lularity, active hemopoiesis, and adequate megakaryooped progressive organomegaly and disseminated intra- cytes. Increased histiocytes were found, with many showing phagocytosed hemopoietic cells; these histiovascular coagulopathy, and died in March 1990. cytes were mature-looking with inconspicuous nucleoli Case 4 and copious pale grey-blue cytoplasm. The reactive A 16-year-old girl presented in June 1990 with a hemophagocytic component was not evident in the initial I-week history of swinging fever and low back pain. marrow specimen from case 3, and was not very promExamination revealed left cervical lymphadenopathy and inent in case 4. Interspersed among the hemopoietic cells and platelets 27 X 10y/l. A diagnosis of “malignant histiocytosis” was made from bone marrow aspirate and lymph node biopsy. The diagnosis was subsequently revised to anaplastic large-cell Ki- 1 lymphoma. The patient refused any treatment and died of the disease after 1 month.
8
114
Case Report: Wong et al.
were small numbers of large lymphoma cells that occurred singly, or rarely in small groups. These lymphoma cells accounted for 1% to 5% of the marrow nucleated cells (Fig. 2). They were variable in size, ranging from being bigger than a promyelocyte to approximating that of a megakaryocyte. They had irregular nuclear folds, open chromatin, multiple prominent nucleoli, and abundant basophilic agranular cytoplasm. Some cells were finely vacuolated particularly in the peripheral rim of the cytoplasm, and some had cytoplasmic blebs. Many exhibited a pale paranuclear Golgi. Rare tumour cells of case 2 exhibited erythrophagocytosis as well (Fig. 3). Marrow biopsies were available for review in cases 3 and 4. The large neoplastic cells were difficult to identify in case 3, and immunostaining with Ber-H2 highlighted this minor population. In case 4, the marrow biopsy obtained from the same site as the aspirate paradoxically showed extensive infiltration by lymphoma cells contrasting with the subtle infiltration in the aspirate smears (Fig. 4). DISCUSSION Anaplastic large-cell Ki- 1 lymphoma rarely involves the bone marrow (Table I), with the reported frequency ranging from 0% to 30.4%. The overall frequency is probably in the region of 10-15%, similar to that reported for diffuse large-cell lymphoma or diffuse large-cell immunoblastic lymphoma [24]. There has been little description in the literature on the marrow aspirate findings of anaplastic large-cell Ki-1 lymphoma [ 1,181 though the marrow biopsy findings have been briefly alluded to [ 1,3,23]. Like the previous reports, the present four cases also demonstrate the subtlety of the lymphomatous infiltrate in the form of isolated cells interspersed among hemopoietic cells. Furthermore, in the series of Delsol et al. [3], two of the five cases were detected to show marrow involvement only by immunostaining for the Ki-1 antigen. Distinction of these large lymphoma cells from megakaryoblasts [25,26] may be at times difficult. The distinguishing features of these large lymphoma cells include the more irregularly folded nuclei, more open but coarse chromatin, multiple prominent nucleoli, more abundant cytoplasm, frequent presence of a pale paranuclear hof, and frequent occurrence of vacuoles. Taken together, these findings are characteristic of anaplastic large-cell lymphoma. Distinction of these large lymphoma cells from histiocytes can also be difficult, but their nuclei and nucleoli are much bigger, and the cytoplasm is much more basophilic. In contrast to most studies, the recent study by Chott et al. 2231 described a high incidence of marrow involvement by Ki-I-positive large-cell lymphoma (seven out of 23 cases). In their report, marrow involvement was limited to those cases exhibiting the group B morphology
(similar to what we delineated as type I morphology [l]) and those occurring in patients over the age of 40 years, and the involvement was sometimes massive. However, in the present series, all the cases with marrow involvement showed type I1 (basophilic cell) morphology. Furthermore, three of the four patients were under 40 years of age. Thus, the morphology of the lymphoma cells cannot be used to predict dissemination of disease, nor is age itself a reliable indicator. Another interesting feature of these four cases is the increase of hemophagocytic histiocytes in the marrow. The finding of atypical mononuclear cells (lymphoma cells) and hemophagocytic cells conforms to the original description of “malignant histiocytosis” [9,27]. However, the cytologically atypical cells in our cases express the Ki-1 antigen and B- or T-lineage markers (except one case) but not histiocytic markers, which does not provide support that they represent histiocytic cells. Neither is erythrophagocytosis by the neoplastic cells (as observed in case 2) pathognomonic of histiocytes, as this phenomenon has been observed in some T-cell lymphomas and in other neoplasms [28,29]. On the other hand, the intermingled bland-looking histiocytes (including the hemophagocytic ones) in the marrow or the lymph node exhibit a histiocytic phenotype (Mac387 and KPl positive, and Ki-1 negative). We interpret these histiocytes as being a reactive component rather than a differentiated component of the neoplastic process, because they are immunophenotypically distinct from the neoplastic cells, they lack cytological atypia, and identical histiocytes are found in reactive hemophagocytic syndrome in the absence of lymphoma. This contention, however, remains to be proven when suitable clonal markers become available. In these examples of malignant lymphoma complicated by reactive hemophagocytosis [6,7,19,30], it is likely that the histiocytic proliferation results from lymphokines secreted by the lymphoma cells, which are probably activated as evidenced by the expression of Ki-1 antigen and other activation markers [ I]. Furthermore, most cases previously reported as “malignant histiocytosis” have now been reinterpreted as examples of malignant lymphoma, mostly of T-cell lineage and with a high frequency of Ki-1 positivity [3,19,30-321. The importance of recognizing the subtle pattern of marrow infiltration in anaplastic large cell Ki-1 lymphoma is three-fold. First, marrow involvement signifies stage IV disease and calls for systemic chemotherapy instead of locoregional therapy which might have been considered as an alternative. As illustrated by case 4, marrow biopsy should always be performed in addition to aspirate. Immunostaining with Ber-H2 (CD30) on paraffin sections of the marrow clot or biopsy is very helpful for picking out the neoplastic cells though the staining may be patchy; plasma cells are also stained but they can be readily recognized as such. We have attempted
Case Report: Ki-Lymphoma in Marrow
Fig. 1. Circulating lymphoma cells in case 3. Note the irregular nuclei, prominent nucleoli, and cytoplasmic vacuoles. Romanowsky. x600.
115
Fig. 2. Medium-power view illustrating the subtlety of the infiltrate. An isolated lymphoma cell (double arrow) is found among the hemopoietic cells. Reactive histiocytes (arrows) with hemophagocytosis are also shown. Romanowsky.
x300.
116
Case Report: Wong et al.
Fig. 3. A-F: Composite figure showing lymphoma cells (A-E) and reactive histiocytes (F). A-C: Lymphoma cells with lobulated nuclei, prominent nucleoli, coarse chromatin, dark-staining cytoplasm, and cytoplasmic blebs. D: Lymphoma cell with a nuclear hole (“doughnut”). Note the
cytoplasmic vacuoles and blebs. E: Lymphoma cells showing erythrophagocytosis. F: Erythrophagocytic histiocytes for comparison. They have smaller nuclei, less coarse chromatin, and indistinct nucleoli. Romanowsky. x 1,250.
Case Report: Ki-Lymphoma in Marrow
Fig. 4. Case 4. A: In the marrow smear, only very rare lymphoma cells (arrows) are identified. Romanowsky. x300. B: Marrow biopsy taken from same site, however, shows extensive infiltration by lymphoma cells. Hematoxylin-eosin. x 400.
117
118
Case Report: Wong et al.
TABLE 1. Frequency of Marrow Involvement in Ki-1 Large-Cell Lymphoma
Report (Ref. No.)”
Frequency
Stein et al., 1985 [51 Kadin et al., 1986 [41 Agnarsson and Kadin, 1988 [2] Delsol et al., 1988 [3] Schnitzer et al., 1988 [ I 11 Tourneau et al., 1988 [12] Weiss et al., 1988 [131 Bejaards et al., 1989 [I41 Chan et al., 1989 (updated in this report) [ I ] Kaneko et al., 1989 [IS] Kaudewitz et al., 1989 [ 161 Tashiro et al., 1989 [17] Kinney et al., 1990 1181 Mason et al., 1990 (191 Rosso et al., 1990 [20] Burns and Dardick, 1990 [21] Bitter et al., 1990 [22] Chott et al., 1990 [23]
Not stated 016 2128 5134 013 014 Not stated 0110 (cutaneous lymphoma) 4124 013 01 15 (cutaneous lymphoma)
2112 2112 1112 015 014 019 7123
4
5
6
7
8. 9.
10.
aOnly those series with more than 2 cases are tabulated. 11.
12.
immunostaining with Ber-H2 on stored methanol-fixed marrow smears by using the alkaline phosphatase antialkaline phosphatase technique, but the results were unsatisfactory. If freshly prepared smears are available, application of the Ki-1 antibody would probably be helpful in identifying the neoplastic population. Second, the few large atypical (lymphoma) cells in the marrow aspirate may represent the first clue to the neoplastic nature of the whole disease process, which should lead to prompt treatment or further investigations as required. Since the patients not uncommonly present with cytopenia, it is likely that bone marrow aspirate or biopsy may represent the first pathologic specimen examined. Third, in patients presenting with hemophagocytic syndrome, the marrow smears and biopsies should be scrutinized for lymphoma cells which may be “hiding” among the hemopoietic cells. Lymphoma would require treatment with cytotoxic drugs, whereas they are contraindicated in infection-associated hemophagocytic syndrome [7,9,33].
13
14
15
16
17
18
19
REFERENCES I . Chan JKC, Ng CS. Hui PK, Leung TW, Lo ESF, Lau WH, McGuire LJ: Anaplastic large cell Ki-l lymphoma, delineation of two morphological types. Histopathology 15: 1 1-34, 1989. 2. Agnarsson BA. Kadin ME: Ki-1 positive large cell lymphoma, a inorphologic and immunologic study of 19 cases. Am J Surg Pathol 121264274. 1988. 3. Delsol G, Saati TA. Gatter KC, Gerdes J , Schwarting R, Caveriviere P, Rigal-Huguet F, Robert A, Stein H , Mason DY: Co-expression of epithelial membrane antigen (EMA), Ki- 1 and interleukin-2 receptor
20
21
by anaplastic large cell lymphomas, diagnostic value in so-called malignant histiocytosis. Am J Pathol 13059-70, 1988. Kadin ME, Sako D, Berliner N, Franklin W, Woda B, Borowitz M, Ireland K, Schweid A, Herzog P, Lange B, Dorfman R: Childhood Ki-l lymphoma presenting with skin lesions and peripheral lymphadenopathy. Blood 68:1042-1049, 1986. Stein H, Mason DY, Gerdes J, O’Connor N, Wainscoat J, Pallesen G, Gatter K, Falini B, Delsol G, Lemke H, Schwarting R, Lennert K: The expression of the Hodgkin’s disease associated antigen Ki- I in reactive and neoplastic lymphoid tissue: Evidence that Reed-Stemberg cells and histiocytic malignancies are derived from activated lymphoid cells. Blood 66348-858, 1985. Jaffe ES, Costa J , Fauci AS, Cossman J, Tsokos M: Malignant lymphoma and erythrophagocytosis simulating malignant histiocytosis. Am J Med 75:741-749, 1983. Chan JKC, Ng CS, Law CK, Ng WF, Wong KF: Reactive hemophagocytic syndrome, a study of 7 fatal cases. Pathology 19:43-50, 1987. Ng CS, Chan JKC, Cheng PNM, Szeto SC: Nasal T cell lymphoma associated with hemophagocytic syndrome. Cancer 58:67-7 1, 1986. Reiner AP, Spivak JL: Hemophagocytic histiocytosis, a report of 23 new patients and a review of the literature. Medicine 67:369-388, 1988. Chan JKC, Ng CS, Hui PK: A simple guide to the terminology and application of leukocyte monoclonal antibodies (Review). Histopathology 12:441-460, 1988. Schnitzer B, Roth MS, Hyder DM, Ginsburg D: Ki-l lymphoma in children. Cancer 61:1213-1221, 1988. Toumeau AL, Andouin J, Diebold J: Ultrastructural study of four cases of Ki-l positive large cell anaplastic malignant lymphoma. Virchows Arch [A] 413:215-222, 1988. Weiss LM, Picker LJ, Copenhaver CM, Wamke RA, Sklar J: Large cell hematolymphoid neoplasms of uncertain lineage. Hum Pathol 191967-973, 1988. Bejaards RC, Meijer CJLM, Scheffer E: Prognostic significance of CD30 (Ki- liBer-H2) expression in primary cutaneous large-cell lymphomas of T-cell origin, a clinicopathologic and immunohistochemical study in 20 patients. Am J Pathol 135:1169-1178, 1989. Kaneko Y, Frizzera G, Edamura S, Maseki N, Sakurai M, Komada Y, Sakurai M, Tanaka H, Sasaki M, Suchi T, Kikuta A, Wasaka H, Hojo H, Mizutani S: A novel translocation, t(2;5)(p23;q35), in childhood phagocytic large T-cell lymphoma mimicking malignant histiocytosis. Blood 732306-813, 1989. Kaudewitz P, Stein H, Dallenbach F, Eckert F, Bieber K, Burg G, Braun-Falco 0: Primary and secondary cutaneous Ki-l + (CD30t) anaplastic large cell lymphomas, morphologic, immunohistologic and clinical characteristics. Am J Pathol 135:359-367, 1989. Tdshiro K, Kikuchi M, Tokeshita M, Yoshida T, Ohishima K: Clinicopathological study of Ki- 1 positive lymphoma. Pathol Res Pract 185:461467, 1989. Kinney MC, Greer JP, Macon WR, Collins RD: Peripheral blood and marrow involvement in Ki-1 anaplastic large cell malignant lymphoma (Abstract). Lab Invest 62:52A2,1990. Mason DY, Bastard C, Rimokh R, Dastugue N, Huret J-L, Kristoffersson U , Magaud J-P, Nezelof C, Tilly H, Vannier J-P, Hemet J, Wamke R: CD30-positive large cell lymphomas (‘Ki-1 lymphoma’) are associated with a chromosomal translocation involving 5q35. Br J Haematol 74:161-168, 1990. Rosso R, Paulli M, Margrini U, Kindl S, Boveri E, Volpato G, Poggi S , Baglioni P, Pileri S: Anaplastic large cell lymphoma, CD30IKi-1 positive, expressing the CD WLeu-MI antigen-Immunohistochemical and morphological relationships to Hodgkin’s disease. Virchows Arch [A] 416:229-235, 1990. Bums FB, Dardick I: Ki- 1-positive non-Hodgkin’s lymphomas-an immunophenotypic, ultrastructural, and morphometric study. Am J Clin Pathol 93:327-332, 1990.
Case Report: Ki-Lymphoma in Marrow 22. Bitter MA, Franklin WA, Larson RA, McKeithan TW, Rubin CM, Le Beau MM, Stephens JK, Vardiman JW: Morphology in Ki-l(CD3O)positive non-Hodgkin’s lymphoma is correlated with clinical features and the presence of a unique chromosomal abnormality, t(2;5)(p23;q35). Am J Surg Pathol 14:305-316, 1990. 23. Chott A, Kaserer K, Augustin I, Vesely M, Heinz R, Oehlinger W, Hanak H, Radaszkiewicz T: Ki-1 positive large cell lymphoma, a clinicopathologic study of 41 cases. Am J Surg Pathol 14:439-448, 1990. 24. Rosenberg SA, Berard CW, Brown BW, Burke J , Dorfman RF, Glatstein E, Hoppe RT, Simon R: National Cancer Institute sponsored study of classification of non-Hodgkin’s lymphomas. Summary and description of a working formulation for clinical use. Cancer 49:21122135, 1982. 25. Williams N, Levine RF: The origin, development and regulation of rnegakaryocytes. Br J Haematol 52: 173-180, 1982. 26. Zucker-Franklin D: Megakaryocytes and platelets. In Zucker-Franklin, Greaves MF, Grossi CE, Marmont AM (eds): “Atlas of Blood Cells-Function and Pathology.” Philadelphia: Lea & Febiger, 1988, pp 619-693. 27. Wamke RA, Kim H, Dorfman RF: Malignant histiocytosis (histiocytic medullary reticulosis), clinicopathologic study of 29 cases. Cancer 35:2 15-230. 1975.
119
28. Kadin ME, Kamoun M, Lamberg J: Erythrophagocytic Ty lymphoma, a clinicopathologic entity resembling malignant histiocytosis. N Engl J Med 304:648-653, 1981. 29. Falini B, Bucciarelli E, Grignani F, Martelli MF: Erythrophagocytosis by undifferentiated lung carcinoma cells. Cancer 46: I 14C1145, 1980. 30. Falini B, Pileri S, De Solas I, Martelli MF, Mason DY, Delsol G, Gatter KC, Fagioli M: Peripheral T-cell lymphoma associated with hemophagocytic syndrome. Blood 75:434444, 1990. 31, Wilson MS, Weiss LM, Gatter KC, Mason DY, Dorfman RF, Warnke RA: Malignant histiocytosis, a reassessment of cases previously reported in 1975 based upon paraffin section immunophenotyping studies. Cancer 66:53&536, 1990. 32. Cattoretti G , Villa A, Vezzoni P, Giardini R, Lombardi L, Rilke F: Malignant histiocytosis, a phenotypic and genotypic investigation. Am J Pathol 136:1009-1019, 1990. 33. Risdall RJ, McKenna RW, Nesbit ME, Krivit W, Balfour HH, Simmons RL, Brunning RD: Virus-associated hemophagocytic syndrome, a benign histiocytic proliferation distinct from malignant histiocytosis. Cancer 44:993-1002, 1979.
