However, the AJCC 8th edition recognizes two prognostic groups in cases of peritoneal disease: stage IVA includes patients with M1a (acellular mucin) and M1b G1 (low-grade atypia); whereas stage IVB groups together patients with M1b G2 (high-grade atypia) and G3 (high-grade atypia with any component of SRCs). Here, MUC5AC is linked to disease of peritoneum.