Noninvasive carcinoma of the gallbladder arising in localized type adenomyomatosis

We report a case of noninvasive carcinoma of the gallbladder arising in the surface mucosa of localized type adenomyomatosis. It was first detected as a polypoid lesion during routine examination with ultrasonography. The gross appearance of the resected specimen showed localized type adenomyomatosis with multiple cysts containing mucin at the fundus of the gallbladder. Microscopic study revealed noninvasive carcinoma in its surface mucosa associated with papillary adenoma in the cyst wall. The occurrence of carcinoma in adenomyomatosis is very rare, and only a few cases have been reported in the literature. Although it has been generally accepted that there is no fear of malignant transformation of adenomyomatosis, the present case suggested that it might be a possible candidate for carcinoma.