T2b Gallbladder Adenocarcinoma Diagnosed by Frozen Section With High-Grade Dysplasia at the Cystic Duct Margin: Diagnostic and Prognostic Considerations.

Gallbladder adenocarcinoma is an uncommon gastrointestinal malignancy that is frequently discovered incidentally during cholecystectomy. Intraoperative frozen section is often used to guide surgical decision-making but has inherent limitations, particularly in assessing depth of invasion. We report the case of a 78-year-old female who underwent an elective laparoscopic cholecystectomy for a gallbladder mass. Intraoperative frozen section demonstrated a tubulovillous adenoma with at least carcinoma in situ. Subsequent permanent histologic evaluation revealed a moderately differentiated adenocarcinoma invading the hepatic-side perimuscular connective tissue, consistent with pT2b disease. Despite the advanced T stage, the tumor exhibited several relatively favorable histologic features, including negative margins and absence of lymphovascular invasion, although nodal assessment was limited. The cystic duct margin showed focal high-grade dysplasia without invasive carcinoma. This case highlights the diagnostic limitations of frozen-section analysis in gallbladder pathology and underscores the importance of integrating final histologic findings when assessing prognosis and postoperative management in T2b disease.