Case 857 -- A 70 year old male with a mass on the right thigh

Contributed by Cecilia Lezcano, MD and Uma N Rao, MD


Male African-American patient in his 70s presented with a non-tender mass on the medial aspect of the distal third of the right thigh that had been present for several years and had recently increased in size.

Physical examination revealed a large subcutaneous tumor measuring 14 x 12 cm that showed an approximately 1 cm bleeding ulcer. The tumor was fixed to the underlying soft tissues.

Patient's past medical history included prostatic adenocarcinoma diagnosed in 2000 and treated with radiotherapy. Local recurrence in 2005 was treated with brachytherapy.


Magnetic resonance imaging of the right lower extremity showed a heterogeneous, avidly enhancing 6.7 x 8.6 x 9.9 cm mass in the distal thigh that did not extend into the deep fascia or involve skeletal muscle (MRI 1). Radiological differential diagnosis included sarcoma, lymphoma, and metastasis.


Needle core biopsies submitted intraoperatively showed small pieces of tissue partly composed of a spindle cell proliferation with necrotic areas (Frozen 100X & 400X). The diagnosis of neoplasm was rendered with consideration of sarcoma within the differential diagnosis. The mass was surgically resected.


Gross examination revealed a well-circumscribed tan-white focally hemorrhagic mass with heterogeneous consistency including firm and soft areas, foci of calcification, and cheesy material suggestive of necrosis. The mass measured 10.9 x 9.7 x 7.4 cm and appeared to abut the overlying skin focally showing a 1 cm ulcer (Mass). The mass was adequately sampled for microscopic examination.


Hematoxylin and eosin sections as well as immunohistochemical stains were evaluated and revealed a neoplastic proliferation located beneath the epidermis composed of sheets and nests of peripheral basophilic to squamoid cells with central eosinophilic shadow ("ghost") cells. There was extensive necrosis, apoptotic debris, and focal areas of calcification. The tumor cells showed a high degree of pleomorphism and numerous atypical mitosis (90 mitoses/10hpf). Calcification and osteoid like foci were focally seen. Foreign body type giant cells surrounded some of the ghost cells. The spindle cell stroma around the solid nests was desmoplastic as well as quite cellular and corresponded to what was found in the frozen section and interpreted as possible sarcoma. The tumor invaded the dermis and subcutaneous adipose tissue. (H&E 40X, 100X.1, 200X.1, 200X.2, 400X).

Immunohistochemical stains revealed that the tumor cells were positive for β-catenin, bcl-2, and AE1/AE3. Ki-67 proliferation index was increased in the viable tumor cells (approximately 70%). The tumor cells were negative for CAM-5.2, CK7, S-100, Melan-A, synaptophysin, CK20, desmin, tyrosinase, actin, and CD34. Stromal spindle cells were positive for actin and focally for desmin. (bcl-2, β-catenin, AE1/AE3, and Ki-67).


Six months after the current excision of the mass the patient presented with multiple nodules in the right groin, the largest measuring 5.6 x 4.1 cm (MRI 2). Fine needle aspiration of the lesion is illustrated in figures Diff-Quik 400X, PAP 400X, cell block 100X, Diff-Quik 400X, 400X.1, bcl-2 LN, and β-catenin LN.


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