TTF1 and neuroendocrine carcinoma: Notably, this case showed diffuse expression of thyroid transcription factor 1 (TTF-1) using both the 8G7G3 and SPT24 clones, alongside immunoreactivity for neuroendocrine markers(CD56, PGP9.5) and focal expression of epithelial markers(AE1/AE3, CAM5.2), This immunophenotypic profile may mimic that of poorly differentiated neuroendocrine carcinoma, contributing to diagnostic confusion.