These included chromogranin A (CHGA) and synaptophysin (SYN) for COID, cytokeratin 5 (KRT5) and p63/p40 (TP63) for SQ, thyroidea trancription factor 1 (TTF1, synonymous with NKX2-1) for AD, and its homolog (NKX2-2) for SCLC (24–28). Here, TTF1 is linked to small cell lung carcinoma.