[Follicular lymphoma with nodular lesions mimicking gallbladder carcinoma]

A 68-year-old female was diagnosed with follicular lymphoma (FL) grade 2, based on the excisional biopsy of her enlarged left cervical lymph node. Positron-emission tomography/computed tomography (PET/CT) revealed the ¹⁸F-fluoro-deoxyglucose-avid lesions in the sigmoid colon and at the fundus of the gallbladder, besides those in the left neck. A sigmoid colon polyp, which was endoscopically resected, proved histologically to be a well- to moderately-differentiated tubular adenocarcinoma with deep invasion into the submucosa. In addition, nodular lesions of the gallbladder were enhanced on dynamic CT, markedly suggesting gallbladder carcinoma. Among FL, colorectal cancer, and presumed gallbladder adenocarcinoma, FL was considered having the lowest priority of treatment because of its indolent nature and low tumor burden. We performed laparoscopic-assisted sigmoid colectomy, followed by gallbladder bed resection on the same day. Unpredictably, gallbladder lesions were histologically revealed to be FL. Often, FL involves extranodal sites such as the gastrointestinal tracts. However, the gallbladder involvement is extremely rare, and preoperative distinction from gallbladder adenocarcinoma remains challenging to date; this report discusses its characteristics along with the literature review. Furthermore, our case, in which another malignant neoplasm coexisted, needed histological identification of the gallbladder lesions to ascertain the therapeutic strategy.