Advanced poorly differentiated gallbladder carcinoma with focal poorly cohesive and signet-ring cell features.

Cases of gallbladder carcinoma containing poorly cohesive and signet-ring cell components are extremely rare, and their clinical characteristics remain unclear. We report a case involving a 70-year-old man who presented with fever and abdominal pain. Imaging at admission revealed diffuse gallbladder wall thickening and peritoneal metastatic nodules around the gallbladder, leading to a diagnosis of advanced gallbladder carcinoma; however, concurrent cholecystitis was suspected because of persistent fever and elevated inflammatory markers. The patient showed no response to antimicrobial therapy or gallbladder drainage, raising concern for tumor-associated inflammation and cancer-related pain. Bile cytology did not yield a definitive diagnosis; the patient showed unusually rapid enlargement of peritoneal metastases and died 2 months after presentation. Autopsy with immunohistopathological analysis confirmed advanced poorly differentiated gallbladder carcinoma with focal poorly cohesive and signet-ring cell features. This case illustrates that rare histological subtypes of gallbladder carcinoma may progress rapidly with extensive peritoneal metastatic nodules. Moreover, in such atypical variants of gallbladder carcinoma, early consideration of oncologic treatment is important while simultaneously controlling the infection.