ULBP2 and primary peritoneal carcinoma: In addition, the study was the first to find that serum MIC-1 and ULBP2 expression was significantly elevated in the PPC patients compared with the NC (P=0.003), while there was no significant difference in CA19-9 between the two groups, suggesting that ULBP2 and MIC-1 could be used for the early diagnosis of PC.