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Case Reports

Abstract

Sarcomatoid transformation is a rare development in the natural history of squamous cell carcinoma, most commonly arising in areas of significant cumulative sun-damage, or rarely in the anogenital region. Herein we report a case of sarcomatoid squamous cell carcinoma (SSCC) arising in an unusual location. A 78-year-old female presented with a slow growing lesion on her mid-abdomen, which had been present for several months. On exam, there was a 3.3 x 3.0 x 2.2 cm erythematous nodule with a filiform stalk. The lesion was shaved at the stalk and electrocautery applied to the base and periphery. Histology showed limited surface epithelium, but where present, demonstrated squamous cell carcinoma in situ. Focal tongues of atypical keratinocytes extended into the dermis, which was extensively replaced by atypical spindle cells and pleomorphic epithelioid cells, with an edematous/myxoid stroma. Immunohistochemistry showed strong and diffuse expression of p63, p40, and CK5/6 in the overt superficial carcinoma component, with scattered, weakly positive pleomorphic epithelioid and spindle cells in the dermis. SOX10, S100, Melan-A, EMA, CD34, SMA, and caldesmon were negative. Subsequent excision showed only a superficial scar and no residual tumor. Exophytic growth appears to be an unusual feature, while loss of pancytokeratin expression is relatively common. p63 and p40 have been reported as sensitive and specific markers, respectively. Exceptional cases can show expression of mesenchymal markers such as SMA. Distinction from histologic mimics - desmoplastic melanoma, leiomyosarcoma, and atypical fibroxanthoma - is necessary, as these have different prognoses and management.