PELISSIER.

1231

SAWAF. AND SHABANA

were demonstrated cally.

grossly rather than microscopi-

Case report of a rare entity and review of the literature. Histopathology ll:953. 1989 3. Batsakis J. Bruner J, Luna M: Polycystrc (dysgenetic) disease of the parotid glands. Arch Otolaryngol Head Neck Surg 114: 1146. 1988

The authors wish to thank Dr Irwin Mandel and the Clinical Research Center for providing the sialochemical data.

4. Mikalyka E: Congenital bilateral polycystic parotid glands. JAMA 181:634. 1962

References

5. Tabak L. Mandel ID. Herrera M. et al: Changes in lactoferrin and other proteins in a case of chronic recurrent parotitis. J Oral Pathol 7:91. 1978

1. Seifert G. Thomsen S. Donath K: Bilateral dysgenetic polycystic parotid glands. Virchows Arch 390:273. 1981 7. Dobson C, Ellis H: Polycystic disease of the parotid glands:

J Oral Maxlllofac 49 1231-1236.

6. Mandel ID. Baurmash H: Sialochemistry in chronic recurrent parotitis: Electrolytes and glucose. J Oral Pathol 9:92, 1980

Surg

1991

Infiltrating Lipoma

(Intramuscular) Benign of the Head and Neck

ALAIN PiLISSIER, DDS, PHD,* MOHAMED H. SAWAF, DDS, PHD,t AND AL-HASSAN M. SHABANA, BDSc, MSc, PHD$

Lipomas are benign soft-tissue mesenchymal tumors commonly occurring in the region of the neck, and less frequently on the back, arm, shoulder, anterior chest wall. breast. thigh, abdominal wall, leg, forehead, and face. in that order,’ Several cases of oral lipomas have been reported. They are generally found in the tongue, buccal mucosa, gingiva, and labial and buccal folds.‘,3 Infiltrating lipoma, also referred to as an intramuscular lipoma. is an unusual form of this benign neoplasm, originating between skeletal muscle bundles and infiltrating through the intramuscular septa. 4-7 These lipomas are generally found on the upper or lower limbs, and are exceedingly rare in the oral cavity. Only six cases have been reported.‘.s-” Because of the rarity of these tumors and their high rate of recurrence without adequate surgery,

Received from the Laboratoire de Biologie-Odontologie. Universite Paris 7. Institut Biomedical de Cordeliers. Paris. * Assistant. Department of Oral Pathology and Surgery. Faculty of Dentistry, Garanciere. t Teaching and Research Associate. Department of Biology. $ Reader, Department of Biology. Address correspondence and reprint requests to Dr Pelissier: Laboratoire de Biologie-Odontologie, Universite Paris 7. lnstitut Biomedical des Cordeliers, Escalier E--2e &age. 15. rue de I’Ecole-de-Medecine. 75270 Paris Cedex 06. Ft?inCe. G

1991 American

Association

of Oral and Maxillofacial

geons 0278-239119114911-0020$3.0010

Sur-

we report the following case of an infiltrating in an unusual oral location.

lipoma

Report of Case The patient was an obese 55-year-old woman who presented in May 1989 to the Department of Oral Pathology and Surgery. Faculty of Dentistry, with a painless swelling involving the lower lip and the left buccal aulcus. She had observed gradual enlargement of the chin at first. then of the lower part of the left cheek. over the 2 previous years. Because of the absence of pain and bleeding. she was not initially alarmed. but 2 years later complained of masticatory problems. There was no history of other tumor masses. no familial antecedents. and her medical health (except obesity) was excellent. Extraoral examination revealed a soft, nontender chin swelling. Intraoral examination showed a large. fixed mass filling the lower sulcus between the right lateral incisor and the left second molar covered by slightly inflamed mucosa. There was an ulceration in front of the left canine due to the pressure exerted by the mass on the tooth (Fig I). The mass was excised in June 1989 under local anesthesia via an oral approach. At surgery the tumor appeared to be lobulated. and partially encapsulated. with a uniform fatty yellow appearance (Fig 3). The anterior part was firmly attached to the surrounding muscles and deeply infiltrated the greater part of the chin up to the superficial cutaneous planes. The mental nerve was involved on the internal side of the tumor (Fig 3). The posterior part was entirely submucosal. with no muscular infiltration. and was easily removed. The tumor was resected completely, together with a thin margin of normal muscle tissue in the anterior part (Fig 4). The gross specimen measured about 7 x 3 x 2.5 cm and weighed 16 g. The wound healed uneventfully. with no functional men-

INFILTRATING

1232

FIGURE I. Clinical appearance at the first consultation. The tumor mass is located in the left vestibule and the lower lip. An ulceration in the region opposite the left canine is seen when the

BENIGN

LlPOMA

during surgical dissection. The FIGURE 3. Clinical appearance infiltrating anterior part is firmly attached to the surrounding muscle>. The mental nerve (arrows) is visible on the internal side of the tumor.

lip is retracted.

tal nerve impairment.

Sutures were removed on the 10th postoperative day. The patient has been recalled at regular intervals. and there has been no recurrence in the last 18 months. Histologically. the tumor was made up of mature fat cells forming lobules, separated by fibrous tissue septa containing some small blood vessels. The fat lobules were covered by an incomplete fibrous tissue capsule and there were skeletal muscle bundles scattered within these lobules (Fig 5). Some of the entrapped muscle fibers had atrophied (Fig 6). There were also areas of nonspecific inflammatory infiltration (Fig 7) and fat necrosis, probably of traumatic origin. None of the cells had atypical nuclei and there was no evidence of malignancy. The diagnosis was submucosal and intramuscular benign lipoma. Discussion Lipomas are well-circumscribed tumors of mature adipose tissue, which may be subdivided into simple lipomas, fibrolipomas, spindle cell lipomas, pleomorphic lipomas, myxoid lipomas, angiolipomas, angiomyolipomas, myelolipomas. lipoblasto-

FIGURE lobulated,

during 2. Clinical appearance with a fatty yellow appearance.

surgery.

The tumor

is

matosis, hibernomas, and atypical lipomas, according to their microscopic features.“‘.” Lipomas may occasionally be deeply seated, growing inter- or intramuscularly. Deep seated intramuscular lipomas (excluding body cavities and viscera) have been termed intramuscular benign lipomas (IBL). of which there are two varieties: Iipomas (the present case) and angiolipomas.’ Paget, in 1853. was the first to describe a lipoma that infiltrated the trapezius muscle.‘.“~” Several other reports were subsequently published; however, the infiltrating character of these lipomas was poorly documented. The first convincing report of IBL was by Hoffman in 1941,14 but it was Regan et al” who defined the entity in 1946, giving the name IBL to these tumors. In 1974 Dionne and Seemayer” reviewed the literature on IBL and added seven cases of their own. A total of 27 tumors were summarized, of which 13 were IBL (lipoma type) and 14 were infiltrating angiolipomas. None of them involved the oral cavity.

FIGURE 4. Gross specimen. The anterior part was resected with a thin margin of normal peripheral muscle tissue because of its infiltrating character. The posterior, submucosal part. was easily removed without any normal tissue.

P~LISSIER.

FIGURE

5.

by fibrous bundles

SAWAF.

AND

Histologic

connective

section

showing

fat lobules

separated

tissue septa. The tissue contains

incompletely

eosin stain. original

1233

SHABANA

covered

by fibrous

magnification

muscle

tissue (hematoxylin-

FIGURE

6.

fibrous X40).

septa

Histologic bundles

section trapped

(hematoxylin-eosin

7.

Section of tumor showing infiltrates

original magnification

leucocytes

of plasma cells

(hematoxylin-eosin

stain,

X80).

X40).

The two first cases of oral IBL (lipoma type) were reported by Bennoff and Wood in 1978.’ There have been only four similar cases reported since then.“,‘-’ 1 The tongue was involved four times,5,x-‘0 the left submandibular area once,x and the superior part of the left cheek once.” The largest tumor was 6 x 4 cm.’ The case reported here is the seventh IBL (Iipoma type) of the oral cavity and the first to be located in the lower lip and buccal sulcus. Moreover, it appears to be one of the largest and the first example (in head and neck) of a tumor extending from a submucosal location to an intramuscular site. No case of IBL (angiolipoma type) in the oral cavity has been reported to date. Oral lipomas and fibrolipomas, in contrast, appear to be rather common. They may account for up to 1.2% of all lipomas’h-‘X and 0.2% to 3.2% of all benign oral tumors.‘“.‘” Hatziotis” and De Vissherlx reviewed 225 oral lipomas and fibrolipo-

in the muscle

FIGURE

and polymorphonuclear

showing within stain.

degenerative

changes

the lipid tissue and the original

magnification

mas reported between 1945 and 1981. They found only I4 cases in the lower lip. These reviews included only soft-tissue lipomas; intraosseous lipomas, of which there were seven cases in the oral cavity, were not considered. While most lipomas are located in the neck region, IBL are rarely found in this area. Stimpson in 1971” was the first to record an 1BL (angiolipoma type) arising adjacent to the thyroid and invading the strap muscles of the neck, followed by Lin and Lin in 1974,” who described two cases of infiltrating angiolipomas among 459 cases of lipomas from all over the body. The first occurred in the supraclavicular region and was associated with brachial plexus invasion: the second was located in the abdomen. No other case of head and neck infiltrating angiolipoma has been recorded since. Matte1 and Persky in 1983” first described an IBL (lipoma type) involving the neck (sternocleidomastoid muscle) and three similar cases were reported in this area since then.“-‘” According to Dionne et al,‘” Varma et al,‘4 and Austin et al’” the sex ratio for the IBL (lipoma type and angiolipoma type) from all over the body is approximately 1: 1. However, other authorsy,23 report that males are more often afflicted than females. Of the seven reported cases of oral IBL. including the present case, males were involved five times and females only twice. If we add the four cases of IBL (lipoma type) involving the neck (Table I), the number of cases in males rises to eight, while there have been only three cases in females. One of the two neck infiltrating angiolipomas occurred in a male and the other in a female. However, the number of cases in the head and neck region is too small for statistical analysis. The female to male ratio for lipomas of Ihe whole body is 3,:1,‘3.‘h,‘8 while oral lipomas occur mainly

1234

in males (60%) and oral fibrolipomas mainly in females (56%).‘*.19 The age of the patients at the time of initial diagnosis shows no clear pattern for IBL, but the majority of cases were adults aged 30 to 60 years 9.‘3~23,1-6 Dionne et alI3 found a mean age of presentation of about 50 years for IBL (lipoma type) and 35.5 years for IBL (angiolipoma type) of the whole body. As shown in Table 1, the mean age for IBL (lipoma type) located in the head is 38.5 years, 45 years for those in the neck, and 41 years for IBL in the head and neck (the mean age is based on the age when the primary tumor was excised). By comparison, 37.7% of oral lipomas, and 41.7% of oral fibrolipomas. occurred in patients aged 40 to 60 years, lx while 58%~of lipomas located in all regions occurred in this age group.’ The size of the oral IBLs was from 1.5 to 7 cm in their greatest diameter, with a mean of 3.5 cm. De Vissher’s found that 54% of the 125 oral lipomas reported were 0.6 to 2 cm across and 20% were between 2 and 3 cm in diameter. Oral IBL (lipoma type) seem to be larger than oral lipomas as far as we can judge from the present series of cases. These deep-seated tumors are generally painless, slow-growing palpable masses that can cause swelling and deformity. The symptoms may be present for several years prior to excision.‘4 Dionne et al,” in their review of nonoral IBL (lipoma and angiolipoma types), found 6 years for the former and 18 years for the latter. Table 1 summarizes the duration of symptoms prior to excision (the primary in case of recurrences) for head and neck infiltrating Table 1.

Head and Neck Infiltrating

Location Oral infiltrating

benign

Left submandibular Tongue Superior Tongue Tongue Tongue Low lip

BENIGN

INFILTRATlNG

Sex

benign

Sternocleido-mastoid Larynx Right posterior Retropharyngeal Neck infiltrating

(I)

Lipomas: Clinical Data Age at Each Excision tyr)

Greatest Diameter (cm)

Duration*

Recurrence(s)

Follow-up Time tmo)

M

II

6

54 months

0

M M M F M

68 5. 7. 8.5 38 56 37

32 3 I.5 2 I .4

NR 2 months NR NR Few weeks

0 2 0 0 0

48 24 I8 25 12 24

F

55

7

24 months

0

I8

M M

9. 18, 29 59

17 1.5

NR 60 months

2 0

18 ‘1

F M

43 69. I?

IO 4

3 months 24 months

0 I

7 ‘)

F M

56 2.5

4 8

18 months 36 months

0 0

I? 24

lipomas muscle

neck benign

lipomas and angiolipomas when this was recorded. Unfortunately, this is imprecise in several cases, ranging from several weeks to 5 years. An increase in the rate of growth noted by the patient is often the reason for medical consultation. On rare occasions, infiltration is so extensive as to cause muscle dysfunction or sensory changes due to pressure on nerve trunks.“.“““.‘” This may cause some pain. A high rate of recurrence is always associated with these tumors. The rate of recurrence for the whole body is reported to be 3%,* 150/c,” or 62.5%,13 with follow-up periods ranging from 4 months to 20 years, and an average of 3 years in the review of Dione et a1.13The time of recurrence also seems to vary from 6 months to 20 years.6.“,‘3.25 These large variations probably depend on the completeness of the excision and perhaps also on the criteria used for diagnosis and distinction from welldifferentiated liposarcoma.9.‘8 Among reported IBL (lipoma type) in an oral location.’ ’ one case recurred twice. One case in the neck recurred onceZS and one twice.” Thus, head and neck IBL (lipoma type) recurred in 27.3% of cases, the rate of recurrence being higher for the neck location (50%) than for the oral site (14.3%). None of the two neck infiltrating angiolipomas were recurrent.“.” This difference confirms that recurrences mainly depend on the totality of the resection. Indeed, these infiltrating tumors are often more deeply seated and more inaccessible in the neck than in the oral cavity. It is interesting to note that the only case of recurrence of an oral IBL may have been due to a difficult surgical access.” In this

lipomas area (8)

(8) part of the left cheek (5) (IO) (9) and buccal sulcus

(this report) Neck infiltrating

LIPOMA

angiolipomas

(21) (22) Abbreviation: NR, not reported. * Duration represents the delay

between

the first symptoms

and the primary

excision.

P~LISSIEK.

SAWAF.

AND SHABANA

case, the second recurrent tumor, which occurred in the infratemporal fossa, has been removed by a median mandibulotomy with a tracheostomy approach for a good access.” For comparison. Ashley’ reported a recurrence rate of less than 1% of lipomas of the whole body, whereas Enzinger”’ found 5%. The only recurrent case in the oral cavity (lower lip) was reported by Clarke (quoted by De Vissher18) in 1981. The IBL may be visible on normal radiographs as a low-density area in comparison with surrounding muscle, and is usually separate from bone.‘.“,” Echography shows only an echogenic mass suggestive of adipose tissue. but does not delineate the boundaries with adjacent structures and muscle bundles.” Xeroradiography has a limited capacity to precisely delineate exact anatomic extents.‘” Computed tomography (CT) scanning appears to be the best way to assess the infiltrating character of IBLs, which are seen as homogenous, very low attenuation masses (usually between -65 and - 125 Hounsfield units) replacing or infiltrating muscle bundles. The margins of the tumor are regular and well-defined, as are the internal septa. Residual peripheral tags of muscle tissue within the lipomatous component are often present, and there are sometimes foci of calcification following hemorrhage within the tumor. Infiltrating benign angiolipomas, in contrast. show mottled areas of high density interspersed with a fat-density lesion because of a prominent vascular component.“’ The boundaries of these neoplasms may not be precisely delineated and they may be confused with liposarcomas on the basis of the CT scan appearance alone. Angiography appears to be the most suitable diagnostic approach for infiltrating benign angiolipomas showing a combination of hypervascularity, poor circumscription, vascular tufts, and enlarged draining veins.30 Histologically, the features of IBL (lipoma type) are distinctive. The tumors are composed of singlevacuole fat cells. The vascular component is inconspicuous, consisting mainly of capillaries. A delicate collagenous connective tissue stroma may be focally present. Fibrous stroma is, in some cases, condensed towards the borders of the neoplasm, forming an incomplete capsule, but usually these tumors are unencapsulated. There is a consistent infiltration, with dissociation of the surrounding muscle fibers. Some of these fibers show degenerative changes.7.“.‘6 Fascia, joint capsules, bones, and nerves may also be infiltrated.’ IBL (angiolipoma type), on the other hand, has a striking predominance of blood vessels and a greater amount of connective tissue mixed with mature fat tissue. The tumor is poorly defined and

1235 there is no capsule. Degenerative changes in the entrapped muscle fibers are also seen. Differential diagnosis with hemangioma (large vessel type) of skeletal muscle is based on the presence of adipose tissue. which forms a large part of the neoplasm. Although muscular invasion is an essential feature, fascia, joint capsules, bones, and nerves may also be infiltrated.‘3.” The main differential diagnostic problem with IBL (lipoma type) is created by liposarcoma. CT imaging is of value in making this distinction. Myxoid and pleomorphic liposarcomas are always more dense than adipose tissue and can easily be distinguished from IBL (lipoma type), but this distinction is more difficult with well-differentiated lipogenic liposarcomas in which the density is essentially that of adipose tissue. However, unlike IBL (lipoma type), these tumors often contain thick streaky areas of increased density and at least one large poorly defined area of increased density.‘4 Histologically, differential diagnosis is based on the absence of multivacuolated lipoblasts characteristic of liposarcomas, hypercellularity, mitoic and hyperchromatic nuclei, cellular pleomorphism, and myxoid degeneration.‘“~“,“~“~” Atypical lipomas have been identified”.3” that contain moderate nuclear atypia and are not easily distinguished from well-differentiated liposarcomas. The atypical lipomas found have been either subcutaneous or deepseated with muscular invasion, but none have been reported in the head and neck region. Nevertheless, liposarcomas are extremely rare in the head and neck.4.” Liposarcomas are thought to arise de novo. although a few isolated cases of malignant transformation within lipomas have been documented. ‘3.34On the other hand, all the reported recurrences of IBL have had a histologic appearance similar to that of the original tumor: no case of malignant transformation has been recorded.h~‘3*‘4,‘s.3-5 The differential diagnosis may include other types of benign lipomatous tumors, such as benign lipoblastomatosis, intermuscular lipoma, lipomatosis. hibernoma, spindle cell lipoma. intramuscular mixoma. and other nonlipomatous formations such as hemangioma (large vessel, small vessel, and mixed types) in which a lipomatous component is sometimes present,“,“.” cyst, hematoma, muscle herniation. fibrous myositis, and hygroma.‘0.‘3.‘47’h All these formations have a distinct and characteristic appearance on CT scans and on histologic examination. Their differentiation from IBL should not pose a diagnostic problem,‘?4 except perhaps for lipomatosis. Indeed, the microscopic appearance of IBL (lipoma type) appears to be very similar to that of lipomatosis, ‘K” with proliferation of mature adipose tissue. unencapsulation. infiltration of mus-

1236 cles and adjacent tissues, no lipoblasts, and a genera1 nonmalignant character. Recurrences after surgery are frequent for both IBL and lipomatosis.‘0*‘8 In fact, lipomatosis is a lesion similar to IBL (lipoma type), but it diffusely involves the subcutis, muscles, and subjacent bones. When the lesion is bilaterally located in the region of the neck, it takes the name of symmetrical lipomatosis. ‘“.23.28 There is a lack of consensus on the pathogenesis of these tumors. According to Das Gupta,3h obesity (as in our case) and local growth of adipose tissue may both be responsible for the formation of a lipoma. This is known as the hypertrophy theory. However, although this explains the formation of a lipoma in a region where there is preexisting fatty tissue, such as the parotid region (presence of the buccal fat pad), limb or trunk, it is less convincing when lipomas develop in areas devoid of preexisting adipose tissue. ‘.3 Ashley’ suggests that the precursors of adipose tissue are tibroblasts. Lipoblasts should not be regarded as separate, unalterable cells, since fatty tissue can be made up from mutable connective tissue cells almost anywhere in the body. The metaplasia theory holds that lipomatous development represents the aberrant differentiation in situ of mesenchymal cells into lipoblasts. In contrast, Lin and Lin” assumed that the lipoma is congenital and arises from embryonic multipotential cells that remain subclinically dormant until they differentiate into fat cells under hormonal influence during adolescence. For them, trauma as a causative factor is believed to be more likely related to discovery than to etiology. However, other?’ suggest that trauma and chronic irritation may trigger the proliferation of soft tissue and play a role in the development of a lipoma. References I. Ashley 2. 3. 4.

5. 6. 7.

DJB: Evans Histological Appearances of Turnouts (ed 3). Edinburgh, Livingstone. 1978. p 54 Shafer WG. Hine MK. Levy BM: Textbook of Oral Pathology ted 3). Philadelphia, PA. Saunders, 1974. p 140 Nanavati SD, Nanavati PS: Solitary subcutaneous lipoma in the parotid region. J Oral Maxillofac Surg 41:5l. 1983 Batsakis JG, Reggi JA. Rice DH: The pathology of head and neck tumors: fibroadipose tissue and skeletal muscle. part 8. Head Neck Surg 3:145. 1980 Garavaglia J, Gnepp DR: Intramuscular (infiltrating) lipoma of the tongue. Oral Surg 63:348, 1987 Mattel SF, Persky MS: Infiltrating lipoma of the sternocleidomastoid muscle. Larynscope 93:205. 1983 Kindblom LG. Angervall L. Stiner B. et al: Intermuscular and intramuscular lipomas and hibernomas: A clinical roentgenologic. histologic and prognostic study of 46 cases. Cancer 33:754, 1974

INFILTRATING

BENIGN

LIPOMA

8. Bennhoff DF, Wood JW: Infiltrating lipomata of the head and neck. Laryngoscope 88:839. 1978 9. Takeda M: Intramuscular lipoma of the tongue: Report of a rare case. Ann Dent 48:22, 1989 IO. Shirasuna K, Saka M, Watatani K, et al: Infiltrating lipoma of the tongue. Int J Oral Maxillofac Surg 18:68, 1989 1 I. Scherl MP, Som PM, Biller HF, et al: Recurrent infiltrating lipoma of the head and neck. Case report and literature review. Arch Otolaryngol Head Neck Surg 112: 1210, 1986 12. Hajdu SI: Pathology of Soft Tissue Tumors. Philadelphia, PA, Lea & Febiger, 1979, p 240 13. Dionne GP, Seemayer TA: Infiltrating lipomas and angiolipomas revisited. Cancer 33:732. 1974 14. Hoffman HOE, Hormley RK: Infiltrating lipoma. Mayo Clin Proc l6:13, 1941 15. Regan JM. Bickel WH. Broders AC: Infiltrating lipomatas of the extremities. West J Surg Gynecol Obstet .54:87, 1946 16. Adair FE. Pack GT. Farrior JH: Lipomas. Am J Cancer 16:1104. 1932 17. Grosh J: Studien iiber das lipom. Dtsch Z Chir 26:307. 1887 18. De Vissher JG: Lipomas and fibrolipomas of the oral cavity. J Maxillofac Surg IO: 177, 1982 19. Hatziotis JC: Lipoma of the oral cavity. Oral Surg 31:5l I, 1971 20. Dockerty MB. Parkhill EM, Dahlin DC, et al: Tumors of the oral cavity and pharynx. Atlas of tumor pathology: section IV. Washington DC. Armed Forces Institute of Pathology. 1968. p 83 21. Stimpson N: Infiltrating angiolipoma of skeletal muscles. Br J Surg 58:464. 1971 22. Lin JJ, Lin F: Two entities in angiolipoma. Cancer 34:720. 1974 23. Chen KTK. Weinberg RA: Intramuscular lipoma of the larynx. Am J Otolaryngol 5:71. 1984 24. Varma DGK, Muchmore JH. Mizushima A: Computed tomography of infiltrating benign lipoma. J Comput Tomogr Il:45. 1987 25. Eisele DW, Landis GH: Retropharyngeal infiltrating lipoma. A case report. Head Neck Surg 10:416, 1988 26. Austin RM. Mack GR: Inliltratina (intramuscular) linomas and angiolipomas. A clinicopathologic study of six cases. Arch Surg I l5:281, 1980 27. Enzinger FM: Benign lipomatous tumors simulating a sarcoma. in Martin, Ayala teds). Management of Primary Bone and Soft Tissue Tumors. Chicago, IL, Year Book Medical, 1977, p II 28. Enzinger FM, Weiss SW: Soft Tissue Tumors ted I). St Louis, MO, Mosby. 1983, p 223 29. Nessi R, Gattoni F. Mazzoni R. et al: Lipoblastic tumors of somatic soft tissues. A xerographic evaluation of 67 cases. Skeletal Radio1 5: 137, 1980 30. Chew FS, Hudson TM, Hawkins IF: Radiology of infiltrating angiolipoma. AJR 135:181. 1980 3 I. Halldorsdottir A. Ekelund L, Rydholm A: CT diagnosis of lipomatous tumors of soft tissues. Arch Orthop Trauma Surg 100:211, 1982 32. Kindblom LG. Angervall L, Fassina AS: Atypical lipoma. Acta Pathol Microbial Immunol Stand A 96:27. 1982 33. Evans HL. Soule EH, Winkelmann RK: Atypical lipoma, atypical intramuscular lipoma and well-differentiated retroperitoneal liposarcoma. Cancer 43574, 1979 34. Sampson CC: Liposarcoma developing in a lipoma. Arch Pathol Lab Med 69:506. 1960 35. Gonzales-Crussi F. Enneking WF, Arean VM: Infiltrating angiolipoma. J Bone Joint Surg 48: I I I I, 1966 36. Das Gupta TK: Tumors and tumor-like conditions of the adipose tissue. Curr Prob Surg I:], 1978 37. MacGregor AB, Dyson DP: Oral lipoma: A review of the literature and report of twelve new cases. Oral Surg 21:770. 1966