title: Primary cutaneous neuroendocrine carcinoma (Merkel cell tumor). An adnexal epithelial neoplasm.
abstract: We report 18 cases of primary cutaneous neuroendocrine carcinoma (CNEC, Merkel cell tumor) that occurred mainly in the sun-exposed skin of elderly patients as dermal and subcutaneous masses of generally monomorphic cells with foci of pronounced pleomorphism. All 18 cases showed immunoreactivity for neuron-specific enolase (NSE), whereas 16 of them showed immunoreactivity for another neuroendocrine marker, protein gene product 9.5 (PGP 9.5). Positivity for PGP 9.5 was more intense and more sharply localized to tumor cells than the staining for NSE. Immunoreactivity for keratins detected by AE1/AE3 and CAM 5.2 monoclonal antibodies was found in 16 and 15 cases, respectively, with prominent paranuclear globular staining. One case stained positively for S-100 protein; all were negative for leukocyte common antigen (LCA). Typical ultrastructural features of neuroendocrine differentiation were noted in all of 14 tumors examined. Morphological and immunohistochemical similarities between these neoplasms and pulmonary small-cell anaplastic carcinoma, now thought to be of bronchial basal cell origin, suggest that CNEC are also derived from epithelium. In addition, their dermal location suggests that this epithelium is likely to be adnexal rather than epidermal.
authors: Department of Pathology, University of Western Australia, Nedlands.
authors: P J
authors: PJ
authors: Heenan
authors: J M
authors: JM
authors: Cole
authors: D V
authors: DV
authors: Spagnolo
mesh_terms: D000291:Adnexal Diseases / Q000473:pathology*; D000368:Aged; D000369:Aged, 80 and over; D015266:Carcinoma, Merkel Cell / Q000473:pathology* / Q000648:ultrastructure; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D009336:Necrosis; D009479:Neuropeptides / Q000032:analysis; D010751:Phosphopyruvate Hydratase / Q000032:analysis; D012878:Skin Neoplasms / Q000473:pathology* / Q000648:ultrastructure; D043222:Ubiquitin Thiolesterase
chemical_list: D009479:Neuropeptides; D043222:Ubiquitin Thiolesterase; D010751:Phosphopyruvate Hydratase