New classification of cystic duct carcinoma

Farrar's criteria for cystic duct carcinoma (histopathologic diagnosis of a carcinoma strictly limited to the cystic duct) are impractical especially when making a diagnosis of primary cystic duct carcinoma in its advanced stage. Therefore, in our previous study, we proposed a new definition of cystic duct carcinoma: a gallbladder tumor, the center of which is located in the cystic duct. In this study, we further propose a new classification for cystic duct carcinomas diagnosed by our definition.

This study included 44 surgical patients with cystic duct carcinoma diagnosed by our criteria. These patients were further classified into two groups: hepatic hilum type (HH, n = 29), in which the tumor mainly invades the hepatic hilum, and cystic confluence type (CC, n = 15), in which the tumor mainly involves the confluence of the cystic duct. The clinicopathologic features of these two groups were analyzed retrospectively.

There was more papillary or well differentiated adenocarcinoma in the CC type lesions than in the HH type. The perineural and vascular invasion were more common in the HH type than in the CC type. The survival rate tends to be higher for patients with the CC type than for those with the HH type (p = 0.064). Moreover, we found a significantly different sex ratio between these two groups (female sex was predominant for the HH type, whereas male sex was predominant for the CC type).

Our new classification showed two distinct types of advanced cystic duct carcinoma, which may help in understanding the clinical characteristics of the carcinoma originated in the cystic duct.