MUC5AC and mucinous adenocarcinoma: • Acellular mucin: mucin without neoplastic epithelial cells• Low-grade mucinous carcinoma peritonei: minor cytologic atypia, sporadic mitosis, “pushing” invasion, strips, gland-like structures or small clusters of cells• High-grade mucinous carcinoma peritonei: more cellular, cribriform growth, high-grade cytological atypia, more mitoses, destructive infiltrative invasion• High-grade mucinous carcinoma peritonei with signet ring cells: any lesion with a component of signer ring cells