Unmasking Coincident Hodgkin Lymphoma and Giant Cell Tumor: Insights from [18F] FDG PET/CT.

Tenosynovial giant cell tumors represent a group of typically non-malignant tumors found within the joints and soft tissues. The occurrence of tenosynovial giant cell tumor alongside hematologic malignancies is an infrequent finding. Herein, we report a patient who presented with coinciding Hodgkin Lymphoma (HL) and tenosynovial giant cell tumor before chemotherapy initiation. The case was discovered during initial assessment using [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography/computed tomography (PET/CT) imaging for HL staging. An unrelated hypermetabolic mass within the left knee joint led to the discovery of this unusual case, which led to a CT-guided biopsy and tenosynovial giant cell tumor discovery. This was clearly demonstrated in interim and end-of-therapy PET/CT studies when all lymphomatous lesions had resolved but the tenosynovial giant cell tumor remained. This case serves as a reminder of the intricate nature of oncological pathology and emphasizes the need for thorough and vigilant diagnostic evaluation for optimal management plan.