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

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.

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.

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.

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".

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.