Extraskeletal Ewing sarcoma

Case contributed by Bahman Rasuli
Diagnosis certain

Presentation

Progressive swelling of right buttock over 3 months.

Patient Data

Age: 30 years
Gender: Female
mri

There is a 10 x 13 x 18 cm large multilobulated intramuscular lesion in the right gluteus maximus that appears hypointense on T1-weighted and hyperintense on T2-weighted and fat-saturated T2-weighted sequences with numerous internal thin septations.

Case Discussion

The mass was surgically resected and histopathology examination revealed:

Microscopic:

Sections show soft tissue neoplasm composed of lobules of tumoral cells with small round nuclei and scant clear cytoplasm which is separated by fibrosis septa and spread in a myxoid stroma and nuclear atypia is noted.

Immunohistochemistry shows positive reactivity for vimentin, BCL2, FLI 1, and CD 99. There was negative reactivity for SMA, EMA, S100, GFAP, PAN-CK, Calponin, P63, and CD 68. TLE 1 is weakly positive in tumoral cells.

Diagnosis:

Histologic features and immunohistochemistry results are consistent with small round cell sarcoma (extraskeletal Ewing sarcoma, myxoid variant).

Extraskeletal Ewing sarcoma is an uncommon soft tissue tumor that is histologically indistinguishable from skeletal Ewing sarcoma.

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