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Neurofilament is superior to cytokeratin 20 in supporting cutaneous origin for neuroendocrine carcinoma
Author(s) -
Stanoszek Lauren M,
Chan May P,
Palanisamy Nallasivam,
Carskadon Shan,
Siddiqui Javed,
Patel Rajiv M,
Harms Kelly L,
Lowe Lori,
Fullen Douglas R,
Harms Paul W
Publication year - 2019
Publication title -
histopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.626
H-Index - 124
eISSN - 1365-2559
pISSN - 0309-0167
DOI - 10.1111/his.13758
Subject(s) - neurofilament , cytokeratin , pathology , merkel cell , merkel cell carcinoma , immunohistochemistry , medicine , biology , carcinoma
Aim Primary cutaneous neuroendocrine carcinoma, or Merkel cell carcinoma ( MCC ), cannot be distinguished morphologically from small‐cell neuroendocrine carcinomas (Sm CC ) from other sites. Immunohistochemistry is required to confirm cutaneous origin, and is also used for detection of sentinel lymph node ( SLN ) metastases of MCC . Cytokeratin 20 ( CK 20) expression is commonly used for these purposes, but is negative in some MCC cases, and has unclear specificity. We evaluated immunohistochemistry for neurofilament and CK 20 in MCC compared with Sm CC from other sites. Methods and results We evaluated neurofilament expression in 55 MCC specimens from 39 unique patients, including nine CK 20‐negative MCC tumours. Neurofilament expression was observed in 42 of 55 (76.4%) MCC cases, including seven of nine (77.8%) CK 20‐negative MCC cases. Neurofilament was expressed in nine of 12 (75%) Merkel cell polyomavirus‐positive tumours and five of 10 (50%) virus‐negative tumours. Compared to a standard immunohistochemical panel (cytokeratin cocktail and CK 20), neurofilament was 87.5% sensitive for detecting SLN metastases. Neurofilament and CK 20 expression was also assessed in 61 extracutaneous Sm CC from 60 unique patients, with primary sites including lung (27), bladder (18), cervix (3), gastrointestinal tract (3), sinonasal tract (2) and other sites (7). The specificity of neurofilament and CK 20 for MCC versus non‐cutaneous Sm CC was 96.7% and 59.0%, respectively. Conclusions Neurofilament has superior specificity to CK 20 in distinguishing MCC from non‐cutaneous Sm CC . Neurofilament is frequently expressed in CK 20‐ and virus‐negative MCC tumours. Limitations of neurofilament immunohistochemistry include lower sensitivity than CK 20 and subtle staining in some tumours. However, our findings indicate that neurofilament is useful for excluding non‐cutaneous Sm CC .