NAPSA and squamous cell carcinoma: Immunohistochemical markers such as TTF-1, Napsin A, P63, P40, CgA, Syn, CD56, and specific cellular features aid in this differentiation.[22] TTF-1 and Napsin A staining typically yield positive results for adenocarcinoma cells, while P63 and P40 are typically positive for squamous carcinoma cells.