[Histopathologic analysis of adenoma and adenoma-related lesions of the gallbladder]

In order to determine the malignant potential of gallbladder adenoma for progression to carcinoma, we evaluated the histopathologic features of adenoma and adenoma-related lesions on cholecystectomized specimens.

Among 1,847 cholecystectomized specimens, 63 specimens from 26 benign adenomas, 9 carcinomas in situ (CIS), and 28 invasive carcinomas were selected. A pathologist reviewed all specimens and selected benign adenomas, CIS in the adenoma, and adenoma residue in invasive carcinomas. Adenomas and adenoma-related lesions were classified according to morphology (tubular, tubulopapillary, and papillary) and the consisting epithelium (biliary, pyloric metaplasia, and intestinal metaplasia). The age and the size of the benign adenomas and carcinomas in the adenoma were also compared.

Adenoma and adenoma-related lesions were found in 34 out (1.8%) of all resected gallbladder. Among 9 CIS and 28 invasive carcinomas, adenoma-related lesions were detected in 7 and 1 case, respectively. All eight carcinomas arising in the adenoma were well-differentiated solitary tumors. The diameters of the carcinomas in the adenoma were, on average, larger than that of the benign adenomas (1.8 cm vs. 0.9 cm, p=0.01). The patients with carcinomas in the adenoma were, on average, older than those with benign adenomas, although the difference was insignificant (57 years vs. 47 years, p=0.09). The morphology and consisting epithelium did not differ between the benign adenomas and carcinomas in the adenoma. The malignant transformation occurred in 23.5% of adenomas.

Gallbladder adenoma is a rare disease, although malignant transformation occurs frequently. Adenoma is a precancerous lesion and the adenoma-carcinoma sequence is one of the gallbladder cancer carcinogenesis.