Yan F, et al. - Researchers investigated the pathological prognostic factors of pseudomyxoma peritonei (PMP), an extremely rare malignancy that is characterized by extensive peritoneal implantation and colloidal ascites. Using H&E and immunohistochemistry, they analyzed specimens from 155 PMP patients. Low-grade mucinous carcinoma peritonei was identified in 63.2% of patients (n = 98), high-grade mucinous carcinoma peritonei in 31.6% (n = 49) and high-grade mucinous carcinoma peritonei with signet ring cells in 5.2% (n = 8). Lymph node metastasis was evident in 9.7% (n = 15); angiolymphatic invasion in 11.6% (n = 18); defective MMR (dMMR) in 6.3% (n = 8); Ki67 labeling index ≥ 50% in 35.5% (n = 55); p53 mutation in 36.1% (n = 56). Univariate analysis identified 10 potential prognostic factors for PMP from the appendiceal origin (n = 140). However, only histologic grade was identified as the independent prognostic factor for OS in multivariate analysis.