Merkel Cell Carcinoma of Lymph Node with an Unknown Primary Cutaneous Tumor - Immunohistochemical Analysis, Differential Diagnosis and Adjuvant Radiotherapy |Biomedgrid

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine neoplasm with a high risk of lymph metastases to regional lymph nodes. Differential diagnosis (DD) imposes immunohistochemical (IHC) analysis to prove the neuroendocrine and epithelial immunotype of the MCC. In a known primary tumor, the primary treatment method is a wide radical excision with a clean resection lines up to 3-5 cm. Selective lymph node dissection is used to confirm the disease stage and proof of regional lymph metastases. The adjuvant post-operative local and regional radiotherapy (RT) in the primary tumor bed and metastatic lymph nodes improves disease-free survival. Against a clinical case with recurrent metastatic lymph nodes from an unknown primary MCC, pathohistological DD difficulties requiring IHC analysis, characteristic aggressive lymph metastasis and the imposed complex treatment, including surgery, chemotherapy and adjuvant RT, are discussed. In order to diagnose the primary tumor, the state of the regional lymph nodes and the presence of distant metastases, the image diagnostic consisting of CT with intravenous contrast and PET/CT, is used.