An updated European organization for research and treatment of cancer (EORTC) protocol for pathological evaluation of sentinel lymph nodes for merkel cell carcinoma (MCC).

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer with a high risk of regional lymph-node metastasis. Accurate pathological evaluation of sentinel lymph nodes (SLN) is therefore critical for staging and clinical management, yet current practices remain heterogeneous across centres. An expert panel within the European Organisation for Research and Treatment of Cancer (EORTC) reviewed available evidence and contemporary practice to develop updated consensus guidance for the pathological assessment of SLN in MCC. The recommendations address specimen handling, lymph-node sectioning strategies, tumour-burden definitions, standardized reporting elements, and a pragmatic approach to ancillary immunohistochemistry (IHC). The proposed protocol provides clear guidance on SLN processing and sectioning to optimize the detection of micrometastatic disease, together with an algorithmic IHC framework that prioritizes sensitive screening markers followed by confirmatory stains to ensure reliable identification of occult nodal involvement. Emphasis is placed on consistent documentation of tumour burden and pN classification to support reproducible reporting and informed clinical decision-making.