FDG PET/CT flip flop phenomenon in treated lymphoma of bone.

A 47-year-old man with primary large B-cell lymphoma of bone underwent an F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) scan for staging. The study demonstrated multiple areas of uptake consistent with osseous lymphoma. After multiple cycles of chemotherapy, a follow-up study demonstrated a dramatic flip flop appearance in which the previously noted areas of osseous lymphoma were photopenic and normal marrow appeared to have increased activity. This flip flop appearance could incorrectly suggest lymphomatous infiltration of normal marrow.