Image Description
Immunohistochemical workup is not necessary for cases with typical small cell morphology. Large cell neuroendocrine carcinomas (LCNECs) have to be distinguished from poorly-differentiated adenocarcinomas or squamous cell carcinomas. LCNECs are diffusely positive for epithelial markers and show variable staining for neuroendocrine markers (chromogranin, synaptophysin, CD56). The image shows CD56 positivity in a small cell carcinoma of gallbladder. The staining for some of the markers may be negative, only focal, or weak. Additional helpful markers include overexpression of p53 and loss of RB1.