Imaging findings of primary bladder MALT lymphoma: A case report

We report the case of a 64-year-old woman diagnosed with primary bladder MALT lymphoma. She was referred to our hospital after body CT during a medical checkup revealed bladder tumors. She had no significant symptoms. Blood tests and urinalysis conducted at presentation showed no abnormalities. Contrast-enhanced CT revealed two tumors protruding into the bladder lumen with smooth margins and broad bases on the posterior wall, exhibiting homogeneous contrast enhancement. On MRI, these tumors showed mild hyperintensity on T2-weighted imaging and marked diffusion restriction on diffusion-weighted imaging, and one tumor was considered to have a stalk. Cystoscopy suggested that the tumors were submucosal. Transurethral resection of the bladder tumor (TUR-BT) was performed with the preoperative diagnosis of bladder cancer due to marked diffusion restriction on MRI. However, the pathological diagnosis was MALT lymphoma. FDG-PET/CT for staging of the lymphoma showed intense FDG uptake in lesions (SUVmax of 20.4 and 24.4) with no significant uptake in other organs indicative of lymphoma involvement. Thus, a final diagnosis of primary bladder MALT lymphoma was made. Distinguishing MALT lymphoma from bladder cancer based solely on CT and MRI findings is challenging. The cystoscopic appearance of a submucosal tumor, along with high SUVmax on FDG-PET and tumor multiplicity, may contribute to the diagnosis of primary bladder MALT lymphoma. If FDG uptake in the tumor bed after TUR-BT is due to a residual tumor, FDG-PET could serve as a useful diagnostic adjunct for an accurate diagnosis. Further studies are warranted to evaluate the utility of FDG-PET for patients with primary bladder MALT lymphoma.