Nuclear medicine techniques in Merkel cell carcinoma: A case report and review of the literature.

Merkel cell carcinoma (MCC) is a rare and aggressive type of neuroendocrine cancer of the skin. It predominantly affects the elderly, with a predilection for the sun-exposed skin of the head and neck. Risk factors include immune-suppressing diseases, such as human immunodeficiency virus (HIV), chronic lymphocytic leukemia and multiple myeloma, organ transplantation, and the presence of the newly-identified Merkel cell polyomavirus (MCPyV). Diagnosis is based on pathological findings, primarily the immunohistochemical determination of cytokeratin 20 positivity. By contrast, staging relies on conventional imaging methods, such as ultrasonography, computed tomography (CT) and magnetic resonance imaging, and nuclear medicine techniques, such as sentinel lymph node scintigraphy, somatostatin receptor scintigraphy (SRS), and positron emission tomography (PET)/CT with 18F-fluorodeoxyglucose (FDG) or alternative radiopharmaceuticals. The treatment of MCC is primarily surgical, with possible adjuvant radiation, while the use of chemotherapy appears to be an alternative therapeutic option that is used only in specific cases. The present study describes the case of a 43-year-old HIV-positive Caucasian man with MCC located on the posterior surface of the left thigh, which was identified by cytological and histological examination of tissue sampled by fine needle aspiration and biopsy performed under CT. SRS demonstrated a high uptake of 111In-diethylene triamine pentaacetic acid-octreotide at the affected site. Therefore, the lesion was surgically excised, and the patient received chemotherapy and adjuvant radiotherapy. Three months subsequent to treatment, the patient underwent a PET/CT scan with 18F-FDG that demonstrated uptake in the cervical lymph nodes and the area of the excised lesion. These findings indicated that the disease was in remission. The aim of the present study was to highlight the value and contribution of nuclear medicine in the diagnosis, staging and follow-up, using PET/CT, octreoscan and sentinel lymph node scintigraphy, of patients with MCC, as well as the therapeutic strategy of radiolabelled somatostatin analogue scintigraphy.