IntroductionClassically defined cystic duct carcinoma is extremely rare owing to its strict diagnostic criteria, which are not suitable in actual clinical settings. Recently, several new classifications of cystic duct carcinoma were reported, which defined it as a tumor with its center located in the cystic duct. On the other hand, the incidence of cystic duct carcinoma, based on the new classifications, is not rare, but all reported cases are advanced.
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