Case of primary low-grade neuroendocrine carcinoma of the skin

A man presents a 4 mm skin tumour at his general practitioner. The tumour is removed on the suspicion of a dermatofibroma. Important differential diagnoses are sebaceous neoplasms, melanomas, Merkel cell carcinomas and large cell neuroendocrine carcinoma, and metastases of neuroendocrine neoplasms from the gut or lung. Immunohistochemical staining excluded sebaceous neoplasm, melanoma and Merkel cell carcinoma, however, was positive for multiple neuroendocrine markers. Relevant scans showed no signs of a primary tumour anywhere else. The final diagnosis was a primary low-grade neuroendocrine carcinoma of the skin. At 30 months follow-up, there was no sign of recurrence.