Comparative Characteristics of Napsin A, TTF 1 and EGFR Mutation Expression in Mucinous Lung Cell Carcinomas.

Background: Invasive mucinous lung adenocarcinomas are rare and account for 2%-10% of all lung adenocarcinoma cases. It is believed that Napsin A exhibits a weaker expression in mucinous adenocarcinomas compared with TTF1, but such correlation is still poorly researched.

Aim: The aim of the study was to determine the frequency of mucinous to nonmucinous adenocarcinomas and compare specificity and sensitivity of monoclonal Napsin A with TTF1 in mucinous adenocarcinomas and define the frequency of EGFR mutations.

Materials And Methods: Eighty-four resected lung carcinomas were prospectively evaluated. All biopsies were analysed with p63, TTF1, monoclonal Napsin A, CK7, CK20 and CDX2 and were studied with real-time PCR technology.

Results: In resected material we detected 49/84 (58.3%) adenocarcinomas and selected 21 mucinous adenocarcinomas out of 46 non-mucinous adenocarcinomas (45.6%). The most common pattern of mucinous adenocarcinomas is papillary - 24% and colloidal - 24%, followed by acinar - 19.2% and lepidic - 19.2%. mNapsin A was positive in 18/21 (85.7%) mucinous adenocarcinomas v/s 17/21 TTF1 positive (80.9%). EGFR mutations were detected in 3/21 cases with mucinous adenocarcinomas (14.3%): mucinous papillary, mucinous acinar and "salivary gland-like".

Conclusion: Our study demonstrates a high proportion of primary mucinous lung adenocarcinomas to primary non-mucinous adenocarcinomas. Sensitivity and specificity of mNapsin A and TTF1 did not show significant difference in pulmonary mucinous and non-mucinous adenocarcinomas, as mNapsin A gave greater sensitivity to mucinous adenocarcinomas. Our results indicate the same mutation frequency of EGFR in mucinous adenocarcinomas as mutation frequency detected in non-mucinous adenocarcinomas in the Bulgarian region.