Immunoexpression of TTF1 and p63 Differentiates Lung Adenocarcinomas in Sputum Samples

CONTEXT: Differentiating NSCLC as either adeno or squamous type and identification of Epidermal Growth Factor Receptor (EGFR) mutations is clinically relevant for lung cancer patients for selecting treatment. Thyroid transcription factor-1 (TTF-1) and p63 were demonstrated as useful markers for histologic typing of lung cancer. Mutation and overexpression of EGFR has been reported in a subset of non-small cell lung cancers. If these markers can be validated for the differential diagnosis of adenocarcinoma in a sputum sample itself, it will be highly beneficial for lung cancer patients. AIMS: To evaluate whether immunocytochemical expression of TTF-1, p63, and EGFR proteins in sputum samples can be used for differential diagnosis of lung adenocarcinoma by comparing with that of the corresponding tissue samples. SETTINGS AND DESIGN: Ninety sputum samples and matched tissue samples were used for the study. SUBJECTS AND METHODS: Monolayered smears and cell blocks of sputum and the corresponding tissue samples were immunostained with the standard ABC method. The expression patterns of these markers were analyzed statistically and compared with clinic-pathological parameters. STATISTICAL ANALYSIS USED: Chi-square test and paired t-test. RESULTS: The p63 protein had a positive expression in 73.9% of SCC whereas TTF1 had positive expression in 75.8% of ADC. The EGFR expression was positive in 27 cases of adenocarcinoma, 21 cases of SCC and 19 cases of NSCLC. CONCLUSIONS: Immunocytochemistry of the aforementioned antibodies in sputum samples can be used as supplementary evidence for the subtyping of NSCLC.