Atypical granular cell tumor-apropos of a case with indeterminate malignant potential.

Malignant granular cell tumor is relatively uncommon, constituting 1%-2% of all granular cell tumors.We describe a case of a 53-year-old woman who presented with a 4.5 X 5.5-cm nodule on her left lower abdomen. An initial punch biopsy revealed a pandermal infiltrate of epithelioid cells with finely granular cytoplasm and vesicular nuclei-histologic features consistent with a granular cell tumor. Given the large size of the neoplasm, an excisional biopsy was recommended that revealed in addition to the above, focal ulceration, epithelioid cells with vesicular nuclei and prominent nucleoli, increased mitotic activity, pleomorphism, and epidermotropism with pagetoid spread-features that were histologically concerning for malignant transformation. We present this case to increase awareness of an uncommon entity and to emphasize the pitfalls associated with incomplete removal and an inadequate biopsy.