Follicular lymphoma of the urachus.

This case report describes an elderly man who presented with mild lower urinary tract symptoms without haematuria. During his workup, an incidental finding of a urachal mass was diagnosed by CT. He underwent robotic partial cystectomy with en bloc urachal excision achieving clear frozen section margins. Histology unexpectedly revealed follicular lymphoma (FL) infiltrating the urachal remnant. This is a unique case of FL of the urachus. The treatment for limited stage disease is either radiotherapy or active monitoring. The 18F-fluorodeoxyglucose positron emission tomography with CT (18F-FDG PET/CT) is considered the gold standard imaging technique for staging FL. The PET/CT demonstrated a single avid right inguinal node. The patient received involved-site radiotherapy (24 Gy) to the pelvis and groin followed by four cycles of rituximab and remains under surveillance. There was no metabolically active nodal or extranodal lymphoproliferative disease on follow-up 18F-FDG PET/CT.