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IAP Case of the Month for August 2015

A 33-year-old male with lump in left thigh back.

Contributed by:

Rasha Salama, M.D.            

IU Department of Pathology and Laboratory Medicine Residency Program, PGY-3

Clinical history:  A 33-year-old male started feeling some discomfort in the posterior aspect of his left thigh back while sitting in 2013. He later developed a lump at the back of his thigh so he finally sought medical care in 2014. His primary care physician at first thought it was bursitis and recommended nonsteroidal anti-inflammatory drugs and physical therapies. However, the mass continued to increase in size and the pain became more significant. An MRI was ordered and showed 12.5 x 14.5 x 18.6 cm enhancing soft tissue mass with multiple septations and central necrosis. The bone did not appear to be involved. The patient also had a chest CT scan that showed several noncalcified subcentimeter lung nodules suspicious for metastatic disease. FNA was performed and diagnosis was rendered. The patient underwent chemotherapy prior to the surgical intervention; however, the treatment did not seem to work and it metastasized to the left inguinal lymph node, right shoulder, left back, and multiple abdominal subcutaneous locations.

Gross Examination:  (Figure 1).

(Figure 2)

Microscopic examination: Histologic sections from the thigh tumor resection

(If you are using Windows PC, right click on the image, open in a new tab and then zoom)

(Hematoxylin-eosin, original magnification _X40)

 (Hematoxylin-eosin, original magnification _X200)

(Hematoxylin-eosin, original magnification _X400)

 (Pan cytokeratin immunostaining, AE1/AE3 (immunoperoxidase, original magnification _X100)

INI-1 immunostaining (immunoperoxidase, original magnification _X40)

(Myogenin immunostaining (immunoperoxidase, original magnification _X40)

S100 immunostaining (immunoperoxidase, original magnification _X40)

Vimentin immunostaining (immunoperoxidase, original magnification _X100)


A-        Melanoma

B-        Epithelioid malignant peripheral nerve sheath tumor

C-        Epithelioid angiosarcoma

D         Epithelioid rhabdomyosarcoma

E-        Epithelioid monophasic synovial sarcoma

F-         Extrarenal rhabdoid tumor

G-        Undifferentiated carcinoma.

H-        Epithelioid sarcoma, proximal type.

Final Diagnosis and Discussion

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