[Invasive micropapillary carcinoma of gallbladder: a clinicopathologic study]

Objective: To study the clinicopathologic features of invasive micropapillary carcinoma (IMPC) of the gallbladder. Methods: Among 160 resected cases of gallbladder adenocarcinomas, the clinical and histological features of gallbladder adenocarcinomas with invasive micropapillary components (IMPC≥5%) were studied. Results: The detection rate of IPMC among gallbladder adenocarcinomas was 19.4% (31/160). Among these 31 cases, the patients' age ranged from 42 to 84 years (mean 64.8 years). The male-to-female ratio was 1∶4.Histologically, 19 cases were characterized by small papillary tufts lacking central fibrovascular cores, lying freely within the clefts of fibrous tissue, resembling IMPC of the breast; in five cases, the micropapillary tufts floated within cystic spaces lined by tumor cells, resembling IMPC of the lung; in four cases, slender, delicate filiform processes on the tumor surface with classic IMPC in the depth of gallbladder was observed; and in three cases mixed features were seen. Small cluster invasion (SCI) was seen adjacent to the IMPC. The lymph node metastatic rate, the lymphovascular invasion rate, and the SCI detection rate were significantly higher in the IMPC group (P=0.000). The IMPC detection rate was related to poorer histological differentiation and increased T stage (P=0.012, C=0.67; P=0.011, C=0.68). The two-year survival rate of IMPC (4/18) was significantly lower than usual gallbladder carcinoma (54.8%, 23/42). Conclusions: Compared to conventional adenocarcinoma of the gallbladder, IMPC has a more advanced tumor status and is prone to lymphovascular invasion and lymph node metastasis, which thus leads to short-term survival. Moreover, SCI may play an important role in the invasion of the IMPC of the gallbladder.