Neoplasm of the skin Merkel cell skin cancer SNOMEDCT_US:254729005 UMLS:C0007129 Neuroendocrine carcinoma of the skin Primary small cell carcinoma of the skin Cutaneous APUDoma Neuroendocrine tumor of the skin Primary undifferentiated carcinoma of the skin A malignant cutaneous tumor of the elderly that is characterized by an aggressive course with regional nodal involvement, distant metastases and a high rate of recurrence. Most patients present with rapidly growing, painless, firm, non-tender, dome-shaped red, occasionally ulcerated skin nodules, which have a red or bluish color, measuring up to several centimeters, on predominantly sun-exposed areas of the body. The overlying skin is smooth and shiny, sometimes exhibiting ulcerative, acneiform or telangiectatic features. SNOMEDCT_US:5052009 Anaplastic carcinoma of the skin Neuroendocrine tumour of the skin Merkel cell cancer of the skin SNOMEDCT_US:253001006 APUdoma