Ewing's sarcoma is a highly malignant, small, round cell tumor that usually affects long bones. The acral part of the extremities is a very rare primary site for this neoplasm.
A fifteen-year-old girl was seen for a lobulated, dome-shaped, 2.7cm diameter, denuded mass on the distal phalanx of the right middle finger which had increased in size over a 14-month period.
The radiological features of the hand showed a cortical brick ofdistal phalanx and surrounding soft tissue mass. Histologically, the biopsy specimen showed sheets of small round to oval cells with scanty cytoplasm, that were closely packed and
separated
into lobules by strands of fibrous tissue. A periodic acid-Schiff stain demonstrated glycogen in the cytoplasm of the tumor cells. Electron microscopy showed large aggregates of glycogen in the cytoplasm of the neoplastic cells.
Immunohistochemical
stains revealed positive staining for vimentin, glial fibrillary acid protein, and neuron specific enolase ; stains for S-100, Factor VIII, and cytokeratin were negative. (Kor J Dermatol 1993 ; 31 (1) : 143-148)
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