Well-differentiated neuroendocrine tumors in skin: Terminology and diagnostic utility of cytokeratin 5/6 and p63

J Cutan Pathol. 2017 Jun;44(6):557-562. doi: 10.1111/cup.12952.

Abstract

Background: Well-differentiated neuroendocrine tumors (WDNETs) in skin include metastases from visceral primary sites and very uncommonly, primary cutaneous carcinoid tumors. Cutaneous WDNET may present a diagnostic challenge and in particular can be mistaken for a benign skin adnexal tumor. In contrast to cutaneous adnexal tumors, metastatic adenocarcinomas to the skin are cytokeratin 5/6 (CK5/6) and p63 negative in the majority of cases. It is unclear if failure to stain with CK5/6 and p63 would be helpful in differentiating WDNETs from cutaneous adnexal neoplasms.

Methods: We reviewed 10 cases of cutaneous WDNETs (8 cases of metastatic disease and 2 presumed primary carcinoid tumors of the skin) and performed immunohistochemical stains for CK5/6 and p63 on all cases.

Results: All 10 cases were negative with both CK5/6 and p63.

Conclusion: Negative staining for CK5/6 and p63 can be helpful to distinguish WDNETs from cutaneous adnexal neoplasms. It is important to consider WDNETs in the differential diagnosis of cutaneous adnexal neoplasms as low-grade tumors may be the first sign of aggressive metastatic disease.

Keywords: CK5/6; cutaneous carcinoid; p63; well-differentiated neuroendocrine tumor.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Aged, 80 and over
  • Female
  • Humans
  • Immunohistochemistry
  • Keratin-5 / metabolism*
  • Keratin-6 / metabolism*
  • Male
  • Middle Aged
  • Neuroendocrine Tumors* / metabolism
  • Neuroendocrine Tumors* / pathology
  • Sweat Gland Neoplasms* / metabolism
  • Sweat Gland Neoplasms* / pathology
  • Terminology as Topic
  • Transcription Factors / metabolism*
  • Tumor Suppressor Proteins / metabolism*

Substances

  • Keratin-5
  • Keratin-6
  • TP63 protein, human
  • Transcription Factors
  • Tumor Suppressor Proteins