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Case Reports

Abstract

A 77-year-old female presented with two nodules on the mid-parietal scalp. The larger lesion had been slowly enlarging for over two years, and the smaller lesion had appeared shortly before biopsy. Initial evaluation diagnosed both as poorly differentiated carcinoma. A metastasis from breast was suggested originally; however, additional investigations did not reveal prior or concurrent breast carcinoma. She underwent excision with Integra placement. One year later, she developed a scalp recurrence. Mammography, PET-CT, and MRI showed no evidence of distant disease. Histology revealed an ulcerated neoplasm with infiltrative pattern present as nests, trabeculae, and single cells in a fibrotic stroma with focal mucin deposition. The nuclei of the tumor cells were uniform to moderately atypical with open granular chromatin, small nucleoli, and scattered mitoses; Ki-67 was 15–25%. Immunohistochemistry showed positivity for CK7, GATA-3, TRPS-1, mammaglobin, ER, PR, and neuroendocrine markers (synaptophysin, chromogranin, INSM-1 [focal]) and negativity for TTF1. While the immunohistochemical profile could have been compatible with metastatic breast carcinoma, the lack of a primary breast lesion and the presence of neuroendocrine features suggested a primary cutaneous sweat gland carcinoma with neuroendocrine differentiation (SCAND). This is a recently recognized rare cutaneous neoplasm that is characterized by epithelial and neuroendocrine differentiation, and variable histologic and immunohistochemical patterns. We present this case to highlight the importance of integrating histopathology and imaging to distinguish rare primary cutaneous tumors from metastatic disease.