Merkel Cell Carcinoma of Lymph Node Without Skin Primary Can - and Should - Be Distinguished from Others Metastatic Neuroendocrine Carcinoma

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Introduction: Merkel cell carcinoma of lymph node without primary tumour (MCCNWP) is a rare tumour which can be misinterpreted as lymph node metastasis (LNM) from a high-grade neuroendocrine carcinoma (NEC) on histological examination. However, this distinction is crucial for therapeutic management.

Aim(s): Establish relevant tools for MCCNWP diagnosis.

Materials and methods: In this retrospective monocentric study, 17 MCCNWP were compared with 17 superficial LNM from other NEC (LNMNEC) (lung=5, thyroid=7, digestive tract=3, other=2). Clinical, morphological and immunohistochemical data (expression of Cytokeratin 7, 19, 20, chromogranin A, TTF1 and Cdx2) were available for all cases. The presence of Merkel cell Polyomavirus (MCPyV) was evaluated in all tumours by immunohistochemistry (CM2B4 antibody directed against MCPyV large t antigen) and PCR.

Conference: 13th Annual ENETSConcerence (2016)

Presenting Author: KERVARREC T

Authors: Kervarrec T, Samimi M, Beby-Defaux A, Touze A, Guyetant S,

Keywords: Merkel cell carcinoma, lymph node, MCPyV,