Answer to Image of the Month August 2015

Submitted by Inchara YK


Tenosynovial giant cell tumor (TSGCT)
Perls stain for iron

Tenosynovial giant cell tumor has several older synonyms: nodular tenosynovitis, benign synovioma, pigmented villonodular synovitis, to list a few. It occurs in young to middle aged adults on the hands and feet.
Microscopically, the lesion comprises of sheets of polygonal cells admixed with osteoclast-like giant cells. Foamy histiocytes and siderophages (Perls positive) are usually present. The nuclei of the mononuclear cells and giant cells are similar in morphology. The lesion may appear hypercellular and mitotically active on occasion, but it is benign biologically. Immunostains for vimentin and CD68 highlight the cells.
The lesion can mimic epithelioid sarcoma sometimes and its typical location and absence of cytokeratin reactivity are helpful in differentiation.


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