Histopathologic classification is not always straightforward; thus, the 2022 WHO classification acknowledges the growing importance of immunohistochemical staining for somatostatin receptors (SSTRs) 2/5, Rb, p53, ATRX, and/or DAXX to distinguish between G3 NETs and NEC. The gene discussed is RB1; the disease is neuroendocrine carcinoma.