False-positive PET/CT for lymphoma recurrence secondary to Langerhans cell histiocytosis.

A 28-year-old man with a history of Hodgkin lymphoma that was intensely [F-18]fluoro-2-deoxy-D-glucose-avid at diagnosis had achieved complete remission following appropriate therapy. On surveillance positron emission tomography/computed tomography (CT), new, intensely [F-18]fluoro-2-deoxy-D-glucose-avid lesions (lytic on CT) were seen within the vertebral body of C7, left scapula, and right glenoid. The findings of a biopsy revealed these lesions to be Langerhans cell histiocytosis. Langerhans cell histiocytosis arising in the context of lymphoma is a well-documented phenomenon, and its appearance on positron emission tomography/CT cannot be conclusively distinguished from lymphoma recurrence. This manuscript emphasizes the necessity of biopsy to ensure correct diagnosis and subsequent correct therapy.