Gallbladder carcinoma with a large monolocular cystic cancerous component

The monolocular cystic formation associated with gallbladder carcinoma is an extremely rare condition. A 79-year-old female suffering from upper abdominal pain and distention was admitted to our hospital. Ultrasonography and computed tomography revealed a monolocular cyst with an irregular wall thickness of 15 cm in diameter concomitant with a solid mass of 8 cm in diameter around the gallbladder bed. During celiotomy, the tumor was found to have a large pale gray cystic component at the fundus of the gallbladder, and disseminated nodules were observed in the peritoneum. We diagnosed the patient with gallbladder carcinoma and performed a simple cholecystectomy that included the tumor without systematic lymphadenectomy. On the cut face of the gallbladder, the lumen was occupied by a solid neoplasm. The cyst included a large amount of serous fluid and protruded continuously from the body of the gallbladder, but it did not communicate with the gallbladder lumen. Although the mechanism responsible for the development of cyst-forming papillary carcinoma of the gallbladder remains unknown, the present case is crucial for understanding the mechanism of cystogenesis in gallbladder carcinoma.