Fertility-Sparing Surgery Holds Its Ground Against a Rare Ovarian Tumor

For young women diagnosed with a seromucinous borderline ovarian tumor, one of the rarest and least understood subtypes of borderline ovarian neoplasm, the central clinical question has long been a deeply personal one: can the ovary be preserved without compromising safety? A new retrospective cohort study from Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, published in the Journal of Ovarian Research, offers some of the most detailed real-world evidence yet on what happens after two common fertility-sparing operations, cystectomy and unilateral salpingo-oophorectomy. The findings are cautiously reassuring, but they also expose how much uncertainty still surrounds this uncommon tumor and how easily follow-up findings can be misread as cancer recurrence.

Seromucinous borderline ovarian tumors, often abbreviated SMBT, occupy an unusual corner of gynecologic pathology. Unlike invasive ovarian carcinomas, borderline tumors are characterized by epithelial proliferation and atypia without destructive stromal invasion, which is why they generally carry an excellent prognosis. What sets the seromucinous subtype apart is its Müllerian-type differentiation, meaning the tumor cells resemble the tissue lining the uterus and fallopian tubes rather than the typical ovarian surface epithelium. Equally striking is the tumor’s frequent coexistence with endometriosis, the inflammatory condition in which uterine-like tissue grows outside the uterus. In the Shanghai cohort, pathologically confirmed endometriosis was present in 35.5 percent of patients, a figure that underscores the biological link between the two diseases and hints at shared pathways of chronic inflammation and hormonal signaling.

Because SMBT is so rare, most of what clinicians know comes from small case series and pooled analyses, leaving the clinicopathological profile and the outcomes of fertility-sparing surgery incompletely defined. The new study, led by Shufeng Kang, Fangfang Xu, and Jialu Yang with corresponding authors Guofang Chen and Shuangdi Li, addressed this gap by assembling a single-center cohort of 186 patients with histologically confirmed seromucinous borderline tumors. The median age at diagnosis was 37.0 years, squarely within the reproductive window, and the median follow-up lasted 35.66 months. Notably, every patient in the cohort had FIGO stage I disease, meaning the tumor was confined to the ovaries at diagnosis, a pattern consistent with the early detection that is typical of borderline lesions.

The researchers compared two surgical strategies. Cystectomy involves shelling out only the cyst while leaving the ovary intact, maximizing hormonal reserve and reproductive potential. Unilateral salpingo-oophorectomy, or USO, removes the entire affected ovary and fallopian tube, trading some reproductive tissue for a theoretically lower risk of leaving abnormal cells behind. Among the 77 patients who underwent cystectomy and the 52 who underwent USO, the team tracked two distinct outcomes that are often conflated in the literature: postoperative imaging-detected adnexal lesions that led to repeat surgery, and histologically confirmed recurrence of borderline ovarian tumor. Separating these outcomes proved to be one of the study’s most important methodological decisions.

The results on repeat surgery were striking. Imaging-detected adnexal lesions prompting a second operation occurred in 40.3 percent of cystectomy patients and 44.2 percent of USO patients, an odds ratio of 0.85 with an exact 95 percent confidence interval of 0.39 to 1.84 and a P value of 0.717. In other words, removing the whole ovary did not meaningfully protect against the need for further surgery compared with simply removing the cyst. Crucially, when the final pathology from these repeat surgeries was examined, the vast majority of the lesions turned out to be non-borderline ovarian cystic lesions, seen in 50 patients, while only four represented histologically confirmed borderline tumor recurrence. This distinction matters enormously for patient counseling, because a woman told she has a new ovarian mass after surgery may fear her tumor has returned, when in fact the lesion is usually a benign functional or hemorrhagic cyst unrelated to malignancy.

When the authors applied a multivariable Cox model to the broader outcome of any postoperative adnexal lesion requiring repeat surgery, cystectomy was not significantly associated with worse outcomes after adjustment, yielding an adjusted hazard ratio of 1.38 with a 95 percent confidence interval of 0.79 to 2.41 and a P value of 0.252. The confidence interval does leave open the possibility of a modestly elevated risk with cystectomy, but the data cannot confirm or exclude that with precision. For histologically confirmed recurrence specifically, the numbers were small and the difference between procedures negligible: recurrence occurred in 2.6 percent of cystectomy patients and 3.8 percent of USO patients, an odds ratio of 0.67 with an exact confidence interval of 0.05 to 9.50 and a P value of 1.000. During the short- to intermediate-term follow-up available, confirmed recurrence was simply uncommon after either operation.

The reproductive findings will resonate most with patients of childbearing age. Among 68 patients with a documented desire for fertility who underwent fertility-sparing surgery, pregnancy and live birth outcomes were remarkably similar across the two procedures. After cystectomy, 16 of 44 women, or 36.4 percent, achieved a documented pregnancy, and the same proportion achieved a documented live birth. After USO, 8 of 24 women, or 33.3 percent, achieved both a documented pregnancy and a documented live birth. The odds ratio comparing the procedures was 1.14 with an exact 95 percent confidence interval of 0.36 to 3.80 and a P value of 1.000. Roughly one in three women conceived and delivered a child regardless of whether the ovary was preserved or removed, a rate that provides a concrete benchmark for counseling, even though the study did not capture every dimension of fertility, such as time to conception, use of assisted reproduction, or ovarian reserve testing.

The authors are careful, and rightly so, about the limits of these comparisons. The study was retrospective and conducted at a single center, meaning treatment allocation was not randomized and surgeon or patient preferences may have influenced which operation each woman received. Follow-up was unequal between groups, the number of confirmed recurrence events was tiny, and fertility-specific data were incomplete. These constraints, the team writes, preclude any conclusions about equivalence, non-inferiority, or comparative long-term oncologic safety between cystectomy and USO. The statistical machinery can show the absence of a detectable difference, but it cannot certify that no difference exists, particularly for an outcome as rare as borderline tumor recurrence, where years more of surveillance may be needed before late events emerge.

Why does this single-institution study matter beyond its own cohort? First, it provides one of the largest series of seromucinous borderline tumors analyzed specifically for post-cystectomy and post-USO outcomes, in a population where the tumor’s association with endometriosis and its uniformly early stage can be documented in detail. Second, it offers a template for how recurrence should be counted in future research: imaging findings and histologically confirmed disease must be reported separately, or the literature will continue to overstate recurrence risk by folding benign postoperative cysts into the same category. Third, the high rate of repeat surgery, around 40 percent in both arms, is itself a clinically actionable signal. It suggests that patients undergoing fertility-sparing surgery for SMBT should be prepared for the real possibility of surveillance imaging, further operations, and the anxiety that accompanies them, even when the ultimate pathology is benign.

The study was approved by the Ethics Committee of Shanghai First Maternity and Infant Hospital and conducted in accordance with the Declaration of Helsinki, with written informed consent waived because de-identified retrospective data were used. It was funded by the Pudong Medical Consortium Project in Shanghai, with no funder involvement in design, analysis, or publication, and the authors declared no competing interests. For the growing community of clinicians managing these Müllerian-type tumors, and for the young women facing the choice between preserving an ovary and removing one, the message is measured but meaningful: both operations appear compatible with low confirmed recurrence and meaningful chances of pregnancy over the follow-up window studied, the choice between them does not yet have a statistically demonstrable winner, and the most common reason a patient returns to the operating room is a benign cyst, not the return of her tumor. Longer follow-up and multi-center collaboration will be needed before either procedure can be declared definitively safer, but this cohort moves the conversation from anecdote toward evidence.

Subject of Research: Oncologic and reproductive outcomes after fertility-sparing surgery for seromucinous borderline ovarian tumors

Article Title: Clinical outcomes after cystectomy or unilateral salpingo-oophorectomy for seromucinous borderline ovarian tumors: a single-center retrospective cohort study

Article References: Kang, S., Xu, F., Yang, J., Jiang, Y., Li, Y., Chen, G., & Li, S. (2026). Clinical outcomes after cystectomy or unilateral salpingo-oophorectomy for seromucinous borderline ovarian tumors: a single-center retrospective cohort study. Journal of Ovarian Research. https://doi.org/10.1186/s13048-026-02298-1

Image Credits: AI Generated

DOI: 10.1186/s13048-026-02298-1

Keywords: seromucinous borderline ovarian tumor, borderline ovarian tumor, cystectomy, unilateral salpingo-oophorectomy, fertility-sparing surgery, recurrence, endometriosis, reproductive outcome, ovarian cancer, gynecologic oncology, retrospective cohort study, FIGO stage I