Malignant small round cell tumor - ulna

Case contributed by Bahman Rasuli
Diagnosis certain


Forearm pain and swelling.

Patient Data

Age: 20 years
Gender: Female

The intramedullary tumor involved nearly the full length of the ulna, with the exception of the proximal olecranon. The surrounding cortex also is involved, and the soft-tissue components at the dorsal and ulnar sides appeared hyperintense due to edema.

Case Discussion

Microscopic appearance is related to malignant round cell tumor.

Tumor necrosis and sheet-like distribution of the neoplastic cells is seen.

The cells have scant cytoplasm, coarse nuclear chromatin and high nuclear to cytoplasmic ratio.

The neoplastic cells also show a strong and diffusive membranous CD99 reactivity.

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