Stage IIIB includes: (T3, N1, M0); (T4, N1, M0). T3: Tumor invades through the muscularis propria into the subserosa or the mesoappendix. T4: Tumor invades the visceral peritoneum, including the acellular mucin or mucinous epithelium involving the serosa of the appendix or mesoappendix, and/or directly invades adjacent organs or structures. N1: One to three regional lymph nodes are positive (tumor in lymph node measuring 0.2 mm or more) or any number of tumor deposits is present, and all identifiable lymph nodes are negative. M0: No distant metastasis. (AJCC 8th ed.) [from NCI]