ANATOMIC PATHOLOGY Original Article
Extraadrenal Myelolipoma A Report of Two Cases STEPHEN B. HUNTER, M.D., 1 ERWIN H. SCHEMANKEWITZ, M.D., 2 CAMERON PATTERSON, M.D., 2 AND VIJAY A. VARMA, M.D. 2
scription. Of possible etiologic significance is the fact that both patients were treated with exogenous steroids. (Key words: Myelolipoma; Soft-tissue neoplasms; Hematopoiesis; Choristoma; Heterotopic tissue) Am J Clin Pathol 1992;97:402-404
Myelolipomas are benign tumors composed of histologically normal hematopoietic elements and adipose tissue. Although some tumors are composed largely of hematopoietic elements, adipose tissue predominates in most cases. The adrenal glands are by far the most common location and rarely show bilateral involvement. Approximately 22 cases of extraadrenal myelolipomas (EAML) have been reported,1"" with more than one half of these cases occurring in the presacral region of the retroperitoneum. Extraadrenal myelolipomas also have been reported in the mediastinum,3 liver,78 stomach,9 leptomeninges,10 and lung." Extraadrenal myelolipomas typically occur as solitary, well-circumscribed masses. The first case presented here is a unique example of multiple EAMLs involving both retroperitoneum and lung, and the second case is a multifocal and poorly circumscribed retroperitoneal EAML.
were present. A routine chest x-ray disclosed four nodular densities. On computed tomographic scan, these appeared as bilateral pleural-based masses, consisting of a combination of fatty- and soft-tissue densities. In addition to these pleural-based masses, additional masses were found in
CASE REPORTS Case 1 A 70-year-old woman was diagnosed with rheumatoid arthritis at age 37 years. During the past 30 years, she was continuously taking prednisone (40 mg/day), and was treated for long periods of time with nonsteroidal antiinflammatory drugs, antimalarials, and gold. Her current medications include prednisone (2 mg/day), aspirin, and aprofloxacin. Her clinical course has been complicated by avascular necrosis of the hips, osteoporosis, vertebral compression fractures, and bilateral cataracts. When she came to our institution, she complained of foot pain. Markedly cushinoid facies as well as severe arthritis in the upper and lower extremities From the ' Veterans Administration Medical Center, Decatur, and the departments of Pathology and Radiology. Emory University School of Medicine, Atlanta, Georgia. FIG. 1 (upper). Computed tomographic scan of bilateral retroperitoneal masses in case 1 with thin, well-defined capsules (open arrows), (lower). Received May 23, 1991; received revised manuscript and accepted for Computed tomographic scan showing one of four pleural-based masses publication June 24, 1991. in case 1. Note the fatty (straight arrow) and soft (curved arrow) tissue Address reprint requests to Dr. Hunter: VA Medical Center (113), components. 1670 Clairmont Road, Decatur, Georgia 30033. 402
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Two cases of extraadrenal myelolipoma with unusual clinicopathologic features are described. The patient in case 1 had multifocal myelolipomas, involving both the lung and retroperitoneum, that mimicked malignancy, and the patient in case 2 had a single diffuse retroperitoneal myelolipoma without circum-
HUNTER ET AL. Extraadrenal Myelolipoma
403
the abdomen by computed tomography: a 0.5-cm left retroperitoneal mass, a 6.5-cm right retroperitoneal mass, and a presacral mass. These well-circumscribed lesions also consisted of varying amounts of fat and soft-tissue density. The normal-appearing adrenal glands were clearly separate from these masses. Physical examination disclosed no visceromegaly or adenopathy. Laboratory tests were remarkable for hemoglobin level of 113 g/L (11.3 g/dL), a hematocrit concentration of 0.36 (36.4%), leukocyte count of 12.3 X 109/L (12.3 X 103/mm3); mean corpuscular volume 79 fl, and platelet count of 635 X 109/L- Results of clinical chemistry tests were within normal limits. Fine-needle aspiration biopsies of one lung nodule and one retroperitoneal mass were performed. Microscopic examination revealed that the tumors were essentially identical, consisting of normal hematopoietic elements, including erythroid cells, myeloid cells, megakaryocytes, and a few lymphocytes, intermixed with mature fat cells (Fig. 1). Several lymphoid aggregates were noted. The tumor was composed of approximately 50% adipose tissue, and the myeloid:erythroid (M:E) ratio was approximately 2:1.
A 63-year-old woman with medical history of hypothyroidism was in her usual state of good health until 1980, when a diffuse sensory and motor neuropathy and bilateral papilledema developed. A spinal tap performed at that time revealed elevated opening pressure and a total protein of 0.97 g/L (97 mg/dL) without pleocytosis. An electromyogram showed decreased conduction velocities consistent with a generalized demyelinating polyradiculoneuropathy. Between 1980 and 1987, the patient was treated with cyclophosphamide (1,100 mg/day) and prednisone (100 mg/day) several times per year with little apparent benefit. In 1987 the patient suffered two cerebrovascular accidents involving the left hemisphere. These were thought to be embolic in nature. Between 1982 and 1989, the patient deteriorated despite cyclophosphamide and prednisone therapy. In April 1985, she was evaluated for shortness of breath and a chest x-ray showed an elevated left hemidiaphragm and an old small left pleural effusion with no infiltrates or cardiomegaly. At this admission, results of her laboratory tests revealed a hematocrit concentration of 0.47 (47.1%), white blood cell count of 12.3 X 109/L (12.3 X 103/mm3), platelet count of 347 X 109/L (347 X 103/mm3), and normal chemistry tests. She was thought to be terminally compromised. No further therapy was offered and she died in June 1989. At autopsy, excessive amounts of adipose and fibrous tissue were present in a patchy distribution throughout the retroperitoneal space, without the formation of discrete masses. This tissue extended from the dome of the urinary bladder to the adrenal glands but did not involve the adrenal glands. Microscopic examination showed that the lesion was composed of approximately 80% adipose tissue and 20% partially confluent islands of trilineage hematopoietic elements. Many broad and thin fibrous bands traversed the tumor and some lymphoid aggregates were encountered. Myeloid, erythroid, and megakaryocyte lines disclosed no significant histologic abnormalities. The M:E ratio was 3:1. The bone marrow was normocellular with normal trilineage hematopoiesis and sparse focal polyclonal plasmacytosis. Additionalfindingsincluded acute interstitial pneumonia, peripheral neuropathy, and an adrenal adenoma. DISCUSSION
Several features demonstrated by our cases of EAML have not been reported previously or emphasized. Pre< FIG. 2 (upper). Fine-needle aspiration biopsy of a retroperitoneal mass in case 1 showing hematopoietic elements and adipose tissue essentially indistinguishable from normal bone marrow. Biopsy of a pleural-based
mass disclosed identical morphologicfindings(hematoxylin and eosin, X260). (lower). Diffuse retroperitoneal myelolipoma in case 2. Two poorly circumscribed foci of hematopoiesis are separated by a thinfibrousband (hematoxylin and eosin, X10).
Vol. 97 • No. 3
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Case 2
404
ANATOMIC PATHOLOGY Article
sentation of myelolipoma as multiple pulmonary and retroperitoneal masses, demonstrated in case 1, appears to be unique. On the basis of the radiologic appearance, this presentation led to a strong but erroneous clinical suspicion of a retroperitoneal malignant condition, possibly liposarcoma, with pulmonary metastasis. Except for a case described by Saleeby1' in 1925, a patient with two pleuralbased pulmonary "heterotopias of bone marrow" without abdominal involvement, we are unaware of documentation of either pulmonary myelolipoma or multiple extraadrenal myelolipomas. In case 2, the retroperitoneal myelolipoma was multifocal and nonencapsulated, in contrast to previously reported EAMLs, which have been uniformly well circumscribed.
Acknowledgments. The authors thank Dr. JefFLichtman, Department of Radiology, Atlanta VAMC, for his assistance with the preparation of this manuscript, and Dr. Anne LeMoine for her editorial contribution. REFERENCES 1. Grignon DJ, Shkrum MJ, Smout MS. Extraadrenal myelolipoma. Arch Pathol Lab Med 1989; 113:52-54. 2. Jagadha V, Ramaswamy G. Extraadrenal myelolipoma. NYS J Med 1985;60. 3. Fowler MR, Alba JM, Williams RB, Byrd CR. Extraadrenal myelolipomas compared with extramedullary hematopoietic tumors: A case of presacral myelolipoma. Am J Surg Pathol 1982;6:363374. 4. Stein SH, Latour F, Frost SS. Myelolipoma arising from ectopic adrenal cortex: Case report and review of the literature. Am J Gastroent 1986;81(10):999-1001. 5. Chen KTK, Felix EL, Ram MS. Extraadrenal myelolipoma. Am J Clin Pathol 1982;78:386-389. 6. Massey GS, Green JB, Marsh WL. Presacral myelolipoma. Cancer 1987;60:403-406. 7. Nishizaki T, Kanematsu T, Matsumata T, Yasunaga C, et al. Myelolipoma of the liver: A case report. Cancer 1989;63:930-934. 8. Mali SPM, Gratama S, Mulder H. Myelolipoma of the liver. Fortschr Rontgenstr 1986; 144:610-611. 9. Le Bodic MF, Mussini-Montpellier J, Magois JY, Lepere J. Myelolipome a localisation gastrique (gastric myelolipoma). Arch Anat Pathol 1974;22:119-122. 10. Nalesnik MA, Martinez AJ, Heros RC. Intracranial lipoma with hematopoietic elements (myelolipoma): Report of a case with successful surgical resection. Cancer 1982;50:295-299. 11. Saleeby ER. Heterotopia of bone marrow without apparent cause. Am J Pathol 1952;1:69-76. 12. Oliva A, Duarte B, Hammadeh R, et al. Myelolipoma and endocrine dysfunction. Surgery 1988;103:711-715. 13. Moskovitz B, Bolkier M, Katz Y, et al. Adrenal myelolipoma stimulating virilizing adrenal tumor. Urol Intern 1988;44:53-55. 14. Kanj HA, Noronha J, D'Aguillo AF, et al. Bilateral adrenal myelolipomas with Cushing's syndrome. JAMA 1988;259:3034-3036. 15. Selye H, Stone H. Hormonally induced transformation of adrenal into myeloid tissue. Am J Pathol 1950; 26:211-244.
A.J.C.P. • March 1992
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Myelolipomas must be distinguished from extramedullary hematopoietic tumors (EHT), which are associated with myeloproliferative disorders or severe anemia. These EHT typically consist of multiple scattered, poorly circumscribed foci of bone marrow elements within the liver, spleen, mediastinum, or subdural space. Extraadrenal myelolipomas are differentiated from EHT on the basis of both gross and microscopic features.3 Previously reported EAMLs, in contrast to EHTs, have been uniformly single, well-circumscribed masses without associated hepatosplenomegaly. Our cases demonstrate that these gross criteria, although useful, do not invariably apply. Extraadrenal myelolipomas may be multifocal or poorly circumscribed lesions, and under these circumstances they sometimes may be mistaken for a malignant neoplasm with metastasis on the basis of clinical and radiologic studies. Microscopically, however, EAMLs and EHTs can be distinguished readily. Extramedullary hematopoietic tumor, in contrast to myelolipoma, is characterized by (1) predominance of hematopoietic elements over adipose tissue, (2) erythroid hyperplasia, and (3) lack of lymphoid aggregates. These histologic features stand in contrast to the features of EAML seen in our cases, i.e., abundant mature fat admixed with scattered islands of hematopoietic tissue and some lymphoid aggregates. The clinical features of our cases also are consistent with EAML. All previously reported cases of EAML have occurred in individuals older than 40 years, usually women, and often with associated obesity, hypertension, or diabetes.3 Our cases were not associated with the severe hematologic abnormalities that are invariably present in EHT. Mild thrombocythemia was present in case 1; however, this is not uncommonly encountered in rheumatoid arthritis. The cause of adrenal and EAMLs has not been elucidated clearly. Perhaps the most widely held theory holds that these tumors arise from choristomatous hemato-
poietic stem cells. Alternatively, it has been suggested that these tumors arise from metaplasia of adrenal cortical cells, either within the adrenal gland or ectopic, or from metaplasia of mesenchymal cells. The stimulus for hematopoiesis is unknown, but a variety of evidence has implicated a role for adrenocorticotrophic or steroid hormones."12 Myelolipomas often are found in patients with features associated with excess Cortisol production, including obesity, hypertension, diabetes, or stressful conditions such as chronic debilitating disease or extensive burns. Myelolipomas have been reported in patients with Conn's syndrome,12 virilization,13 and Cushing's syndrome.14 Finally, injection of a crude pituitary adrenocorticotrophic hormone extract into rodent adrenal glands has been shown to induce differentiation of adrenal cortical tissue into hematopoietic elements.15 The two cases in the present report, both treated with long-term corticosteroids, suggests that exogenous steroids also may play a role in the pathogenesis of some cases of EAML.
Extraadrenal Myelolipoma A Report of Two Cases STEPHEN B. HUNTER, M.D., 1 ERWIN H. SCHEMANKEWITZ, M.D., 2 CAMERON PATTERSON, M.D., 2 AND VIJAY A. VARMA, M.D. 2
scription. Of possible etiologic significance is the fact that both patients were treated with exogenous steroids. (Key words: Myelolipoma; Soft-tissue neoplasms; Hematopoiesis; Choristoma; Heterotopic tissue) Am J Clin Pathol 1992;97:402-404
Myelolipomas are benign tumors composed of histologically normal hematopoietic elements and adipose tissue. Although some tumors are composed largely of hematopoietic elements, adipose tissue predominates in most cases. The adrenal glands are by far the most common location and rarely show bilateral involvement. Approximately 22 cases of extraadrenal myelolipomas (EAML) have been reported,1"" with more than one half of these cases occurring in the presacral region of the retroperitoneum. Extraadrenal myelolipomas also have been reported in the mediastinum,3 liver,78 stomach,9 leptomeninges,10 and lung." Extraadrenal myelolipomas typically occur as solitary, well-circumscribed masses. The first case presented here is a unique example of multiple EAMLs involving both retroperitoneum and lung, and the second case is a multifocal and poorly circumscribed retroperitoneal EAML.
were present. A routine chest x-ray disclosed four nodular densities. On computed tomographic scan, these appeared as bilateral pleural-based masses, consisting of a combination of fatty- and soft-tissue densities. In addition to these pleural-based masses, additional masses were found in
CASE REPORTS Case 1 A 70-year-old woman was diagnosed with rheumatoid arthritis at age 37 years. During the past 30 years, she was continuously taking prednisone (40 mg/day), and was treated for long periods of time with nonsteroidal antiinflammatory drugs, antimalarials, and gold. Her current medications include prednisone (2 mg/day), aspirin, and aprofloxacin. Her clinical course has been complicated by avascular necrosis of the hips, osteoporosis, vertebral compression fractures, and bilateral cataracts. When she came to our institution, she complained of foot pain. Markedly cushinoid facies as well as severe arthritis in the upper and lower extremities From the ' Veterans Administration Medical Center, Decatur, and the departments of Pathology and Radiology. Emory University School of Medicine, Atlanta, Georgia. FIG. 1 (upper). Computed tomographic scan of bilateral retroperitoneal masses in case 1 with thin, well-defined capsules (open arrows), (lower). Received May 23, 1991; received revised manuscript and accepted for Computed tomographic scan showing one of four pleural-based masses publication June 24, 1991. in case 1. Note the fatty (straight arrow) and soft (curved arrow) tissue Address reprint requests to Dr. Hunter: VA Medical Center (113), components. 1670 Clairmont Road, Decatur, Georgia 30033. 402
Downloaded from http://ajcp.oxfordjournals.org/ by guest on June 5, 2016
Two cases of extraadrenal myelolipoma with unusual clinicopathologic features are described. The patient in case 1 had multifocal myelolipomas, involving both the lung and retroperitoneum, that mimicked malignancy, and the patient in case 2 had a single diffuse retroperitoneal myelolipoma without circum-
HUNTER ET AL. Extraadrenal Myelolipoma
403
the abdomen by computed tomography: a 0.5-cm left retroperitoneal mass, a 6.5-cm right retroperitoneal mass, and a presacral mass. These well-circumscribed lesions also consisted of varying amounts of fat and soft-tissue density. The normal-appearing adrenal glands were clearly separate from these masses. Physical examination disclosed no visceromegaly or adenopathy. Laboratory tests were remarkable for hemoglobin level of 113 g/L (11.3 g/dL), a hematocrit concentration of 0.36 (36.4%), leukocyte count of 12.3 X 109/L (12.3 X 103/mm3); mean corpuscular volume 79 fl, and platelet count of 635 X 109/L- Results of clinical chemistry tests were within normal limits. Fine-needle aspiration biopsies of one lung nodule and one retroperitoneal mass were performed. Microscopic examination revealed that the tumors were essentially identical, consisting of normal hematopoietic elements, including erythroid cells, myeloid cells, megakaryocytes, and a few lymphocytes, intermixed with mature fat cells (Fig. 1). Several lymphoid aggregates were noted. The tumor was composed of approximately 50% adipose tissue, and the myeloid:erythroid (M:E) ratio was approximately 2:1.
A 63-year-old woman with medical history of hypothyroidism was in her usual state of good health until 1980, when a diffuse sensory and motor neuropathy and bilateral papilledema developed. A spinal tap performed at that time revealed elevated opening pressure and a total protein of 0.97 g/L (97 mg/dL) without pleocytosis. An electromyogram showed decreased conduction velocities consistent with a generalized demyelinating polyradiculoneuropathy. Between 1980 and 1987, the patient was treated with cyclophosphamide (1,100 mg/day) and prednisone (100 mg/day) several times per year with little apparent benefit. In 1987 the patient suffered two cerebrovascular accidents involving the left hemisphere. These were thought to be embolic in nature. Between 1982 and 1989, the patient deteriorated despite cyclophosphamide and prednisone therapy. In April 1985, she was evaluated for shortness of breath and a chest x-ray showed an elevated left hemidiaphragm and an old small left pleural effusion with no infiltrates or cardiomegaly. At this admission, results of her laboratory tests revealed a hematocrit concentration of 0.47 (47.1%), white blood cell count of 12.3 X 109/L (12.3 X 103/mm3), platelet count of 347 X 109/L (347 X 103/mm3), and normal chemistry tests. She was thought to be terminally compromised. No further therapy was offered and she died in June 1989. At autopsy, excessive amounts of adipose and fibrous tissue were present in a patchy distribution throughout the retroperitoneal space, without the formation of discrete masses. This tissue extended from the dome of the urinary bladder to the adrenal glands but did not involve the adrenal glands. Microscopic examination showed that the lesion was composed of approximately 80% adipose tissue and 20% partially confluent islands of trilineage hematopoietic elements. Many broad and thin fibrous bands traversed the tumor and some lymphoid aggregates were encountered. Myeloid, erythroid, and megakaryocyte lines disclosed no significant histologic abnormalities. The M:E ratio was 3:1. The bone marrow was normocellular with normal trilineage hematopoiesis and sparse focal polyclonal plasmacytosis. Additionalfindingsincluded acute interstitial pneumonia, peripheral neuropathy, and an adrenal adenoma. DISCUSSION
Several features demonstrated by our cases of EAML have not been reported previously or emphasized. Pre< FIG. 2 (upper). Fine-needle aspiration biopsy of a retroperitoneal mass in case 1 showing hematopoietic elements and adipose tissue essentially indistinguishable from normal bone marrow. Biopsy of a pleural-based
mass disclosed identical morphologicfindings(hematoxylin and eosin, X260). (lower). Diffuse retroperitoneal myelolipoma in case 2. Two poorly circumscribed foci of hematopoiesis are separated by a thinfibrousband (hematoxylin and eosin, X10).
Vol. 97 • No. 3
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Case 2
404
ANATOMIC PATHOLOGY Article
sentation of myelolipoma as multiple pulmonary and retroperitoneal masses, demonstrated in case 1, appears to be unique. On the basis of the radiologic appearance, this presentation led to a strong but erroneous clinical suspicion of a retroperitoneal malignant condition, possibly liposarcoma, with pulmonary metastasis. Except for a case described by Saleeby1' in 1925, a patient with two pleuralbased pulmonary "heterotopias of bone marrow" without abdominal involvement, we are unaware of documentation of either pulmonary myelolipoma or multiple extraadrenal myelolipomas. In case 2, the retroperitoneal myelolipoma was multifocal and nonencapsulated, in contrast to previously reported EAMLs, which have been uniformly well circumscribed.
Acknowledgments. The authors thank Dr. JefFLichtman, Department of Radiology, Atlanta VAMC, for his assistance with the preparation of this manuscript, and Dr. Anne LeMoine for her editorial contribution. REFERENCES 1. Grignon DJ, Shkrum MJ, Smout MS. Extraadrenal myelolipoma. Arch Pathol Lab Med 1989; 113:52-54. 2. Jagadha V, Ramaswamy G. Extraadrenal myelolipoma. NYS J Med 1985;60. 3. Fowler MR, Alba JM, Williams RB, Byrd CR. Extraadrenal myelolipomas compared with extramedullary hematopoietic tumors: A case of presacral myelolipoma. Am J Surg Pathol 1982;6:363374. 4. Stein SH, Latour F, Frost SS. Myelolipoma arising from ectopic adrenal cortex: Case report and review of the literature. Am J Gastroent 1986;81(10):999-1001. 5. Chen KTK, Felix EL, Ram MS. Extraadrenal myelolipoma. Am J Clin Pathol 1982;78:386-389. 6. Massey GS, Green JB, Marsh WL. Presacral myelolipoma. Cancer 1987;60:403-406. 7. Nishizaki T, Kanematsu T, Matsumata T, Yasunaga C, et al. Myelolipoma of the liver: A case report. Cancer 1989;63:930-934. 8. Mali SPM, Gratama S, Mulder H. Myelolipoma of the liver. Fortschr Rontgenstr 1986; 144:610-611. 9. Le Bodic MF, Mussini-Montpellier J, Magois JY, Lepere J. Myelolipome a localisation gastrique (gastric myelolipoma). Arch Anat Pathol 1974;22:119-122. 10. Nalesnik MA, Martinez AJ, Heros RC. Intracranial lipoma with hematopoietic elements (myelolipoma): Report of a case with successful surgical resection. Cancer 1982;50:295-299. 11. Saleeby ER. Heterotopia of bone marrow without apparent cause. Am J Pathol 1952;1:69-76. 12. Oliva A, Duarte B, Hammadeh R, et al. Myelolipoma and endocrine dysfunction. Surgery 1988;103:711-715. 13. Moskovitz B, Bolkier M, Katz Y, et al. Adrenal myelolipoma stimulating virilizing adrenal tumor. Urol Intern 1988;44:53-55. 14. Kanj HA, Noronha J, D'Aguillo AF, et al. Bilateral adrenal myelolipomas with Cushing's syndrome. JAMA 1988;259:3034-3036. 15. Selye H, Stone H. Hormonally induced transformation of adrenal into myeloid tissue. Am J Pathol 1950; 26:211-244.
A.J.C.P. • March 1992
Downloaded from http://ajcp.oxfordjournals.org/ by guest on June 5, 2016
Myelolipomas must be distinguished from extramedullary hematopoietic tumors (EHT), which are associated with myeloproliferative disorders or severe anemia. These EHT typically consist of multiple scattered, poorly circumscribed foci of bone marrow elements within the liver, spleen, mediastinum, or subdural space. Extraadrenal myelolipomas are differentiated from EHT on the basis of both gross and microscopic features.3 Previously reported EAMLs, in contrast to EHTs, have been uniformly single, well-circumscribed masses without associated hepatosplenomegaly. Our cases demonstrate that these gross criteria, although useful, do not invariably apply. Extraadrenal myelolipomas may be multifocal or poorly circumscribed lesions, and under these circumstances they sometimes may be mistaken for a malignant neoplasm with metastasis on the basis of clinical and radiologic studies. Microscopically, however, EAMLs and EHTs can be distinguished readily. Extramedullary hematopoietic tumor, in contrast to myelolipoma, is characterized by (1) predominance of hematopoietic elements over adipose tissue, (2) erythroid hyperplasia, and (3) lack of lymphoid aggregates. These histologic features stand in contrast to the features of EAML seen in our cases, i.e., abundant mature fat admixed with scattered islands of hematopoietic tissue and some lymphoid aggregates. The clinical features of our cases also are consistent with EAML. All previously reported cases of EAML have occurred in individuals older than 40 years, usually women, and often with associated obesity, hypertension, or diabetes.3 Our cases were not associated with the severe hematologic abnormalities that are invariably present in EHT. Mild thrombocythemia was present in case 1; however, this is not uncommonly encountered in rheumatoid arthritis. The cause of adrenal and EAMLs has not been elucidated clearly. Perhaps the most widely held theory holds that these tumors arise from choristomatous hemato-
poietic stem cells. Alternatively, it has been suggested that these tumors arise from metaplasia of adrenal cortical cells, either within the adrenal gland or ectopic, or from metaplasia of mesenchymal cells. The stimulus for hematopoiesis is unknown, but a variety of evidence has implicated a role for adrenocorticotrophic or steroid hormones."12 Myelolipomas often are found in patients with features associated with excess Cortisol production, including obesity, hypertension, diabetes, or stressful conditions such as chronic debilitating disease or extensive burns. Myelolipomas have been reported in patients with Conn's syndrome,12 virilization,13 and Cushing's syndrome.14 Finally, injection of a crude pituitary adrenocorticotrophic hormone extract into rodent adrenal glands has been shown to induce differentiation of adrenal cortical tissue into hematopoietic elements.15 The two cases in the present report, both treated with long-term corticosteroids, suggests that exogenous steroids also may play a role in the pathogenesis of some cases of EAML.
