Personalized treatment of
lung cancer requires an accurate subclassification of
non-small cell lung carcinoma (NSCLC) into
adenocarcinoma (ADC),
squamous cell carcinoma (SqCC), and other subtypes. In poorly differentiated
tumors especially on small fine-needle aspirate specimens, the subclassification could be difficult in certain cases. Our previous study using resected
tumor tissue has shown that the combination of commonly used individual markers (
thyroid transcription factor 1 [TTF-1], P40, and Napsin A) into a novel triple marker has high sensitivity and specificity in subclassification of NSCLC and also the advantage of using minimal
tumor tissue. In this study, we further evaluated the utility of this novel triple marker using fine-needle aspirate cases. We included primary NSCLC, consisting of 37 SqCCs (primary, 35;
metastasis, 2) and 50 ADCs (primary, 29;
metastasis, 21), 12 metastatic ADCs of nonpulmonary primary, and 10 small cell lung
carcinomas. The immunohistochemical patterns were semiquantitatively scored. In lung SqCCs and ADCs, the sensitivity and specificity of the triple marker were 100% and 97.1% and 86.0% and 100%, respectively. The triple marker showed no immunoreactivity in 12 metastatic nonpulmonary ADCs. In 10 small cell lung
carcinomas, TTF-1 had focal positivity in 40% of cases. The limitations of the triple marker include staining of alveolar macrophages (by TTF-1 and Napsin A), basal layer of bronchial epithelial cells (by P40), and nonspecific cytoplasmic staining of TTF-1. Our study not only supports our previous finding using resected
tumor specimens but also provides evidence that the triple marker can be used for cytological material and preserving
tumor tissue for molecular testing.