Lymphoid hyperplasia with a polyp form of the gallbladder macroscopically mimicking carcinoma

Lymphoid hyperplasia is a type of tumor-like hyperplasia of lymphoid tissue. There have been few reports on lymphoid hyperplasia of the gallbladder. Here, we report a case of lymphoid hyperplasia with a polyp form of the gallbladder macroscopically mimicking carcinoma. Liver dysfunction was diagnosed in a 75-year-old woman who presented with a gallbladder mass measuring 20 mm during an annual health checkup. Antibody tests for infectious diseases were positive for anti-HBs and anti-HBc antibodies. Accordingly, a laparoscopic cholecystectomy was performed. Macroscopically, the mass was a papillary/sessile tumor (29 × 25 mm) located in the fundus of the gallbladder. Histologically, the tumor was accompanied by an erosion on a portion of the surface layer, while the remaining epithelium showed regenerative changes and mild hyperplasia. No atypia was observed in the constituent epithelium. Hyperplasia of the polarized lymphoid follicles was observed in the interstitium, and tingible body macrophages were scattered in the germinal center. Immuno-histologically, the germinal center showed CD20 positivity, weak CD10 positivity, Bcl-2 negativity, and a high Ki-67 index (MIB-1). These findings suggested that the proliferating lymphoid follicles were reactive rather than neoplastic. Therefore, we diagnosed the patient with lymphoid hyperplasia of the gallbladder and chronic cholecystitis.