Abstract:

Merkel cell carcinoma (MCC) is a very rare high-grade neuroendocrine carcinoma that is frequently located in the skin. Although most cases are associated with Merkel cell polyomavirus, there are also cases in which the virus cannot be detected. The purpose of presenting the case of MCC with primary nodal involvement is due to its rare presentation. A 59-year-old male patient presented to the hospital with painless mass in the neck. Imaging analyses revealed necrotic lymphadenopathies on the neck, measuring up to 4.5 cm in size. After an explorative surgery with preliminary diagnoses of lymphoma and squamous cell carcinoma , samples taken from the excised mass showed high-grade neuroendocrine carcinoma morphology. In addition to neuroendocrine markers, CK7 and CK20 positivity were observed in the immunohistochemical tests performed. The patient was diagnosed with primary nodal MCC due to the negativity of the markers performed to exclude other malignancies and the absence of a different focus on PET imaging analysis outside the lymph node. The differential diagnosis of MCC should be kept broad due to the histopathological morphology of small round cell malignant tumors. In high-grade neuroendocrine carcinomas, the possibility of MCC should be ruled out especially if CK20 positivity is present. Although is has been reported that primary nodal MCC cases have a better clinical course compared to nodal metastatic cases with a known primary, there are limited case series studies on this topic. A multisystem approach is recommended for proper clinical management.