Evaluation of the value of thyroid transcription factor (TTF-1) and P63 in subtyping of non-small cell lung cancer in cytologic material.This is a retrospective study including 40 cases of primary lung lesions who underwent image guided FNAC from pulmonary nodules. The final histopathologic diagnosis was the gold standard. Cell blocks were stained with anti-TTF-1, and P63. Nuclear immunoreactivity for both markers was considered specific. Sensitivity, specificity, positive and negative predictive values, of the cytologic diagnosis and of the two markers, as well as the accuracy of the combined markers were calculated.Cytomorphology achieved a sensitivity of 83.3%, specificity of 91%, PPV of 91%, and NPV of 83.3%, for the diagnosis of AC, and 91% sensitivity, 83.3% specificity, 83.3% PPV, and 91% NPV, for the diagnosis of SCC. The concordance between cytologic and histopathologic diagnoses of AC and SCC was 87%. TTF-1 achieved 87.5% sensitivity, 94.7% specificity, 95.5% PPV, and 85.7% NPV for AC, while P63 achieved 94.7% sensitivity, 95.8% specificity, 94.7% PPV, and 95.8% NPV for SCC. TTF-1 enhanced the sensitivity of cytomorphology for AC from 83.3% to 87.5%, and specificity from 91% to 94.7%. Similarly P63 enhanced the sensitivity for SCC from 91% to 94.7%, and specificity from 83.3% to 95.8%.TTF-1 achieved moderate sensitivity, and high specificity in the diagnosis of AC, while P63 was highly sensitive and specific for the diagnosis of SCC. Immunocytochemistry raised the sensitivity and specificity of FNAC in diagnosing AC and SCC using TTF-1 and P63, respectively.