For serous borderline tumors (SBTs) localized to the ovary (Stage 1), including those with foci of microinvasion, the survival is 100% (the same as women in general population). These patients may develop recurrences or bowel wall adhesions requiring surgical intervention. With non-invasive peritoneal implants, the survival is greater than 95%. About 5% of the SBTs progress to low-grade serous carcinoma. The remaining 95% pursue a benign or an indolent course. The presence of microinvasive foci in otherwise typical serous borderline tumor does not appear to worsen the prognosis significantly. The presence of focal areas with typical features of serous carcinoma (high-grade nuclear features) in an otherwise typical serous borderline tumor does worsen the prognosis significantly and makes it similar to that of pure serous carcinoma. The image shows a high power view of a SBT with hierarchical branching pattern of papillae. The tips of papillae have cell clusters that appear detached. Occasional mitotic figures can be seen.