Mucin-containing Rokitansky-Aschoff sinuses with extracellular mucin deposits simulating mucinous carcinoma of the gallbladder.

Rokitansky-Aschoff sinuses (R-As) are epithelial invaginations that extend down the gallbladder wall through the smooth muscle gaps and by this pathway they reach the subserosal connective tissue. We report here 5 cases of mucin-containing R-As that ruptured, and as a result, extracellular mucin escaped into the adjacent stroma. They were compared with 10 mucinous carcinomas of the gallbladder. Three cases of mucin-containing R-As accompanied by abundant extracellular mucin deposits with epithelial strips, glands and papillary structures were misinterpreted as mucinous carcinomas. Because of this, the patients were subjected to a second unnecessary radical surgical procedure. In the remaining 2 cases, the extracellular mucin associated with R-As was acellular and regarded as focal. Three patients were men and 2 women whose ages ranged from 2 to 71 years (average age 52 y). The youngest patient was a 2-year-old boy in whom the mucin-containing R-As were discovered incidentally by magnetic resonance imaging. He was later diagnosed with metachromatic leukodystrophy. The remaining 4 patients complained of right upper quadrant pain and had a thickened gallbladder wall identified by computed tomography and magnetic resonance imaging. There were gallstones in 3 patients. The R-As located in the lamina propria contained mucin but were not cystically dilated whereas those located in the subserosa were mucin-filled and often cystically dilated. Detached fragments of biliary epithelium, small glands, and papillary structures lacking cytologic atypia and mitotic figures were identified in the abundant mucin deposits located in the subserosa of 3 cases. The overlying surface gallbladder epithelium exhibited papillary hyperplasia with focal intestinal metaplasia in 2 patients, one of which had metachromatic leukodystrophy. The lack of reactivity for carcinoembryonic antigen and p53 and the low proliferative activity as measured by MIB-1 labeling index provided additional support to the benign nature of the lesion. Clues to separate mucin-containing R-As from mucinous carcinoma are provided. All 5 patients with mucin-containing R-As are disease free 8 months to 7 years after surgery (median follow-up of 39 mo).