MUC5AC and MUC5B enhance the characterization of mucinous adenocarcinomas of the lung and predict poor prognosis.

Aims From the viewpoint of histogenesis, lung adenocarcinoma can be subdivided into two groups: terminal respiratory unit (TRU) and non-TRU types. We recently reported a non-TRU type adenocarcinoma designated as ciliated adenocarcinoma (we now prefer central type adenocarcinoma). We suggest reasons that mucinous adenocarcinoma should encompass central type adenocarcinoma to represent its biological characteristics as non-TRU type adenocarcinoma. Methods and results Mucin (MUC)5AC and MUC5B were expressed more significantly in non-TRU type adenocarcinoma (P < 0.01). Thirty-five (76.1%) and 45 cases (97.8%) of 46 non-TRU type adenocarcinoma showed positivity for MUC5AC and MUC5B. Twelve (7.6%) and eight (5.1%) cases of 157 TRU type adenocarainoma showed positivity for MUC5B and MUC5AC. NKX2-1 gene expression was measured with quantitative reverse transcription–polymerase chain reaction (qRT–PCR). ΔΔCt of NKX2-1 gene expression was 6.79 for TRU type adenocarcinoma and 0.6 for non-TRU type adenocarcinoma. Overall survival and disease-free survival were poorer in non-TRU type adenocarcinoma (P = 0.02 and P = 0.03). A multivariate test also showed that non-TRU type adenocarcinoma is an independent prognostic factor (P = 0.04). Conclusion MUC5AC and MUC5B were specific makers for non-TRU adenocarcinoma, including both central type adenocarcinoma and mucinous adenocarcinoma. We suggest that non-TRU type adenocarcinoma presents a poorer prognosis, so it should be regarded separately from TRU type adenocarcinoma.