Claudin-1 is linked to presence of implants and micropapillary pattern in serous borderline epithelial tumours of the ovary

Aims Expression of Claudin-1 has been associated with prognosis in several cancers. Here we investigated the expression pattern of Claudin-1 in borderline tumours of the ovary (BOT). Methods We analysed a cohort of 114 cases of borderline tumour (BOT). Claudin-1 expression was studied by immunohistochemistry using a polyclonal antibody and was compared with clinical and histopathological characteristics. Results Strong Claudin-1 expression was found in 30 cases (26.3%) independent of histological subtype. Expression was significantly less frequent in International Federation of Gynecology and Obstetrics (FIGO) stage I (p=0.045), while the presence of microinvasion did not correlate with Claudin-1 expression. In contrast, we detected a highly significant association of Claudin-1 expression with the presence of peritoneal implants (p=0.003) and micropapillary pattern (p=0.047), which are features exclusively seen in serous BOT. Moreover, when we restricted our analysis to the subtype of serous BOT, the association of Claudin-1 expression with peritoneal implants (p<0.001) and micropapillary pattern (p=0.003) remained highly significant. Conclusions In conclusion, Claudin-1 expression is associated with the presence of peritoneal implants and micropapillary pattern, which have been shown to be associated with poor prognosis. We speculate that overexpression of Claudin-1 might be linked to the mitogen-activated protein kinase pathway activation in BOT and suggest further studies to define its prognostic and potential therapeutic value.