A Case of Fluorine-18-Fluorodeoxyglucose Positron Emission Tomography/ Computed Tomography Findings of Mycosis Fungoides with Large Cell Transformation Involving Cutaneous Lesions, and Metastasis to Lymph Node and Viscera

Large cell transformation (LCT) of mycosis fungoides (MF) is a histopathological transformation of neoplastic small lymphocytes with a clonally identical large cell phenotype, which is found in 20%–50% of cases of advanced MF. Some few cases and studies have been reported about the role of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18FFDG PET/CT) in diagnosing MF-LCT. This is a case of a 55-year-old man who had a left neck mass for 4–5 months. He underwent excisional biopsies on the skin and soft tissue. The histopathologic report showed MF-LCT. The 18F-FDG PET/CT findings revealed hypermetabolic lesions in the skin, cervical lymph node, and visceral organ. We introduce a rare case of MF-LCT involving both cutaneous and extracutaneous lesions.