A 63-year-old man underwent a (18)F-fluorocholine ((18)F-FCH) PET/CT for staging assessment of a high-risk locally advanced prostate cancer with an equivocal node on conventional workup (Gleason 4 + 5, PSA 11.1; T3b, N(0/1), M(0) on standard staging investigations). (18)F-FCH-avid disease was demonstrated in the prostate and several non-enlarged pelvic nodes. An incidental focus of tracer uptake was reported within the left lobe of the thyroid gland, with subtle enlargement of the left thyroid lobe on the CT component of the study. A diagnosis of diffuse large B-cell lymphoma was confirmed following thyroid ultrasound and cytology.