The expression of TTF1, CDX2 and ISL1 in 74 poorly differentiated neuroendocrine carcinomas

CDX2 and TTF1 demonstrate potential utility in suggesting the primary site of PDNEC. In addition, CDX2 may be useful in supporting the diagnosis of LCNEC in cases with overlapping or borderline morphology. Utility of ISL1 as an adjunctive diagnostic marker of SmCC remains to be studied.