Non–small cell lung carcinoma with diffuse coexpression of thyroid transcription factor-1 and ΔNp63/p40

Summary Here, we present a case of non-small cell lung carcinoma (NSCLC) with widespread and strong nuclear immunopositivity for both thyroid transcription factor-1 (TTF-1) and ΔNp63/p40 (p40). Double immunofluorescence for TTF-1 and p40 showed co-expression of both markers in the tumor cells. Furthermore, PTEN (pHis123Asp) and TP53 (pVal272Leu) mutations were identified as possible mitogenic driver mutations by next-generation sequencing. To the best of our knowledge, this is the first case of NSCLC harboring concurrent PTEN and TP53 mutations with widespread and strong coexpression of TTF-1 and p40, which has been confirmed in the resected specimen, and only the second documented case of NSCLC with TTF-1 and p40 diffuse coexpression in the carcinoma cells from the same individual. Our case illustrates the possibility that poorly differentiated NSCLCs with widespread and strong nuclear positivity for TTF-1 and p40 may be an under recognized and new entity.