Heterogeneity of large cell carcinoma of the lung: an immunophenotypic and miRNA-based analysis

Large cell carcinomas (LCCs) of the lung are heterogeneous and may be of different cell lineages. We analyzed 56 surgically resected lung tumors classified as LCC on the basis of pure morphologic grounds, using a panel of immunophenotypic markers (adenocarcinoma [ADC]-specific, thyroid transcription factor-1, cytokeratin 7, and napsin A; squamous cell carcinoma [SQCC]-specific, p63, cytokeratin 5, desmocollin 3, and Δnp63) and the quantitative analysis of microRNA-205 (microRNA sample score [mRSS]). Based on immunoprofiles 19 (34%) of the cases were reclassified as ADC and 14 (25%) as SQCC; 23 (41%) of the cases were unclassifiable. Of these 23 cases, 18 were classified as ADC and 5 as SQCC according to the mRSS. Our data show that an extended panel of immunohistochemical markers can reclassify around 60% of LCCs as ADC or SQCC. However, a relevant percentage of LCCs may escape convincing immunohistochemical classification, and mRSS could be used for further typing, but its clinical relevance needs further confirmation.