NCAM1 and neuroendocrine carcinoma: Cluster of differentiation 56 (CD56), also known as neural cell adhesion molecule (NCAM) and initially identified as antigen Leu-19, is expressed across various normal cell types and tumor entities, including natural killer (NK) cells, neural cells, myogenic progenitor cells, NK cell lymphomas, and neuroendocrine carcinomas [2,3,4].