Abstract

We present the case of an 87-year-old male who presented with a nodule on his scalp. The initial biopsy showed a dermal-based neoplasm of medium to large cells with ample eosinophilic cytoplasm and prominent granular cell features, including large eosinophilic granules with clear halos. Minimal pleomorphism was present and no significant areas of spindle cell morphology were appreciated. A single dermal mitosis was identified. There was no significant expression of S100, SOX-10, CD34, desmin, smooth muscle actin, pancytokeratin, p63 or ALK-1. A descriptive diagnosis was rendered at this time, with a differential consisting of a non-neural granular cell tumor versus an atypical fibroxanthoma/pleomorphic dermal sarcoma with granular cell features. During excision via Mohs micrographic surgery, the lesion was found to extend deeper into the subcutis. Routinely processed specimens from the excision showed the deeper aspect of the tumor to have significantly more pleomorphism, cytologic atypia, frequent mitoses, and prominent areas of spindle cell morphology. The diagnosis of pleomorphic dermal sarcoma with granular cell features was rendered in accordance with the histologic, immunophenotypic, and clinical findings. This case illustrates a potential diagnostic pitfall with superficial biopsies of pleomorphic dermal sarcoma or atypical fibroxanthoma with granular cell features and a non-neural granular cell tumor. Given the aggressive course a pleomorphic dermal sarcoma can follow, especially when compared to a non-neural granular cell tumor, caution is advised when encountering a dermal neoplasm with deceptively bland cytology with granular cell features which does not express S100.

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