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Case Reports

Abstract

An 85-year-old woman presented to her primary care physician with a slowly growing, palpable subcutaneous mass of the left lateral upper back. The mass was initially believed to be benign, and the patient was referred to dermatology clinic. Punch biopsy was performed, and histopathologic examination revealed a cellular but relatively monotonous spindle cell proliferation within the deep subcutis. Tumor cells were discohesive and arranged in fascicles with abundant dermal hemorrhage. The chromatin pattern was fine and dispersed. Mitotic activity measured 8 per 10 high power fields. Initial work-up found the lesional cells to be positive for pancytokeratin, partially positive for CK7, and negative for SOX-10 and Mart-1, leading to a preliminary diagnosis of spindle-cell squamous cell carcinoma.  The case was sent in consultation to our institution for additional work-up. Due to the abundant extravasated red blood cells, CD31, ERG, and HHV8 were ordered and were all negative, ruling out a vascular neoplasm. Chart review revealed a past diagnosis of atypical carcinoid tumor of the lung, and the lesional cells were found to express synaptophysin and chromogranin, confirming neuroendocrine differentiation, with weak/patchy positivity for CK7 and TTF-1 positivity, supporting lung origin. The diagnosis of atypical carcinoid tumor, metastatic to the skin, was made. Atypical carcinoid tumors are defined as neuroendocrine tumors with 2-10 mitoses per 2 mm² or foci of necrosis. This case reminds dermatopathologists that neuroendocrine tumors (particularly carcinoid and atypical carcinoids) may demonstrate spindled morphology and lack the high grade features seen in neuroendocrine carcinomas.