Double immunostaining for maspin and p53 on cell blocks increases the diagnostic value of biliary brushing cytology

Our objective is to elucidate the usefulness of maspin/p53 double immunostaining on biliary brushing cytology specimens. We first examined the expression of maspin in the biliary epithelium with variable degrees of dysplasia using surgically resected specimens (n = 56). Maspin appeared to be overexpressed in a stepwise manner from benign to malignant cholangiocytes: the reactive epithelium (20%), biliary intraepithelial neoplasia (~50%), and invasive cholangiocarcinomas (>90%). Next, an automated sequential double immunostaining protocol for maspin and p53 was applied to paraffin-embedded cell blocks of the biliary brushing cytology specimens obtained from 58 consecutive patients. Cell block preparation was successful in 44 cases (76%), which were morphologically diagnosed as adenocarcinoma (n = 16), atypical cells not diagnostic for malignancy (n = 10), and benign (n  = 18). Double positive cells were observed in 14/16 (88%) morphologically malignant, 6/10 (60%) borderline, and 0/18 benign cases. All 20 positive cases were proven to have pancreatobiliary malignancies by subsequent imaging or pathological analyses. A similar staining protocol for S100P and p53 was also applied to the same cohort; however, the positive frequency was slightly lower than those of maspin and p53 (36% vs. 45%). In conclusion, Maspin/p53 double immunostaining on cell blocks contributes to the detection of malignant cells in biliary brushing cytology specimens.