Claudin18.2 expression and its clinicopathological feature in adenocarcinoma from various parts

Aims To clarify claudin18.2 expression and its clinicopathological features in various cancers, especially in lung adenocarcinoma. Methods Immunohistochemistry staining and fluorescence in situ hybridisation (FISH) were performed to detect claudin18.2 expression and CLDN18 gene rearrangement in adenocarcinoma from different organs. Results The results showed that claudin18.2 expression was found in 68% (27 of 40) of lung mucinous adenocarcinoma, 52% (16 of 31) of cholangiocarcinoma, 2% (10 of 423) of colorectal adenocarcinoma tissue microarray, 27% (6 of 22) of colorectal mucinous adenocarcinoma and 30% (3 of 10) of cervical adenocarcinoma, but not in all 39 cases of invasive breast adenocarcinoma by immunohistochemistry staining. There was significantly positive correlation between ratio of claudin18.2-positive carcinoma cells and staining intensity in lung mucinous adenocarcinoma and cholangiocarcinoma. Claudin18.2 expression was much more in female patients than male patients with lung mucinous adenocarcinoma. In addition, cholangiocarcinoma with claudin18.2 expression was more aggressive and had perineural invasion. Intraductal papillary neoplasm of the bile duct and epithelial dysplasia of the adjacent bile in cholangiocarcinoma also showed claudin18.2 expression. All three cases of cervical adenocarcinoma with claudin18.2 expression were moderately differentiated adenocarcinoma including one human papillomavirus (HPV)-associated carcinoma, two non-HPV-associated and gastric-type carcinoma. CLDN18 gene rearrangement was not found in all 22 cases with high claudin18.2 expression by FISH. Conclusions Our results suggest claudin18.2 might be a potential biomarker for targeted therapy on lung mucinous adenocarcinoma, cholangiocarcinoma, colorectal mucinous adenocarcinoma and gastric-type cervical adenocarcinoma.