Introduction Disseminated peritoneal leiomyomatosis (DPL) is a rare, benign smooth muscle proliferative disorder. It is characterized by multiple peritoneal nodules that may mimic peritoneal carcinomatosis or leiomyosarcoma on imaging and are frequently detected incidentally during surgery. The pathogenesis of DPL is incompletely understood and is considered multifactorial. Iatrogenic dissemination following laparoscopic morcellation or hysteroscopic electrosurgery may result in the peritoneal implantation of leiomyoma fragments. Hormonal factors, including pregnancy and exogenous estrogen exposure, are also implicated.1,2 Experimental studies suggest that steroid hormones induce peritoneal mesenchymal hyperplasia, while estrogens promote fibroblast proliferation and nodule formation; notably, lesion regression has been observed after the reduction of hormonal stimulation. Additionally, the chemotactic migration of subperitoneal mesenchymal stem cells may contribute to tumor development.2,3 DPL is a rare condition with a limited global literature, and its diagnosis during pregnancy is particularly infrequent.4 Some cases were identified during emergency cesarean sections for pregnancy-related abdominal pain, whereas others were incidentally detected during routine examinations or elective cesarean delivery.2,5–9 DPL should be distinguished from intravenous leiomyomatosis, parasitic leiomyoma, and benign metastasizing leiomyoma, which are characterized by intravascular extension and distant organ involvement, respectively.2,10 Although DPL is generally benign, rare cases of malignant transformation have been described. No standardized diagnostic or management guidelines for DPL are currently available. The impact of the condition on pregnancy outcomes and the optimal management strategy during gestation remain unclear. We report a case of recurrent DPL during pregnancy following a prior laparoscopic myomectomy and summarize the obstetric characteristics and follow-up outcomes of pregnancy-associated DPL cases to provide a basis for clinical management. Case presentation In 2017, a patient underwent ultrasonography for menorrhagia, which revealed a 98 mm × 82 mm × 87 mm intramural uterine leiomyoma (Supplementary Fig. 1, https://links.lww.com/MFM/A134). The patient subsequently underwent laparoscopic myomectomy. During the procedure, the tumor was morcellated and extracted using an electric morcellator, whether a containment bag was used was not specified. Pathological examination confirmed that the specimen was a smooth muscle tumor of uterine origin. Postoperative follow-up ultrasonography showed no abnormal findings. On March 20, 2019, the patient was admitted for a cesarean delivery due to a prior uterine scar. Intraoperatively, dense adhesions were observed between the greater omentum and the anterior abdominal wall. A firm nodular lesion, measuring approximately 20 mm × 50 mm × 15 mm, was identified on an adhesive band between these structures. The lesion was resected for pathological examination (Supplementary Fig. 3, https://links.lww.com/MFM/A134). Histological analysis (hematoxylin and eosin staining) demonstrated spindle-shaped tumor cells arranged in fascicles with mild cytologic atypia; mitotic figures were rare (approximately 1–2 per 5 mm2), and no necrosis was identified. Immunohistochemical analysis showed that the cells were positive for actin, desmin, and succinate dehydrogenase complex iron sulfur subunit B (SDHB), and negative for CD117, CD34, DOG-1, and S-100; the Ki-67 index was less than 1%. Thereafter, the patient remained under annual outpatient follow-up without further abnormalities. In 2022, pelvic ultrasonography identified a pelvic mass measuring approximately 48 mm × 31 mm × 36 mm, which was considered likely to represent a leiomyoma (Supplementary Fig. 4, https://links.lww.com/MFM/A134). In 2024, ultrasonography showed an interval enlargement, with the mass now measuring 66 mm × 37 mm × 51 mm (Supplementary Fig. 4, https://links.lww.com/MFM/A134). Pelvic MRI demonstrated a solid mass in the left posterior region of the uterus, suggestive of a smooth muscle tumor involving the left broad ligament (Fig. 1).Figure 1.: Pelvic MRI performed on January 9, 2024. The yellow arrow indicates a well-defined mass in the left posterior uterus, which measures approximately 59 mm × 43 mm × 37 mm. A T1WI showed an isointense signal. B T2WI displayed a heterogeneous, slightly hyperintense signal. C T2-FS at the identical level (same slice as Fig. 1B). MRI: Magnetic resonance imaging; T1WI: T1-weighted imaging; T2WI: T2-weighted imaging; T2-FS: T2-weighted fat-suppressed.In 2024, at 11+5 weeks of amenorrhea, ultrasonography revealed an early intrauterine pregnancy with a gestational age of 12+2 weeks. A subserosal uterine mass measuring 86 mm × 55 mm was noted at the posterior wall. Prenatal examinations remained unremarkable. At 38+1 weeks of gestation, the patient was admitted for a cesarean section. During abdominal exploration, a mass of approximately 8 cm × 8 cm × 7 cm was identified on the surface of the sigmoid mesentery, alongside multiple scattered nodules (each measuring approximately 0.5 cm). The gastrointestinal surgery team assisted in the resection of these lesions for pathological evaluation (Fig. 2). Immunohistochemical analysis showed that the cells were positive for actin, desmin, and PR, and negative for CD117, DOG-1, CD34, S-100, and ER; they also showed positivity for SDHB, with a Ki-67 index of approximately 1% (Supplementary Fig. 4 and 5, https://links.lww.com/MFM/A134). Based on the histomorphology, immunophenotype, and the patient’s clinical history, the lesions were consistent with disseminated peritoneal leiomyomatosis. A subsequent ultrasound scan conducted on May 12, 2025, revealed a minimal amount of blood in the uterine cavity, with no evidence of pelvic lesions.Figure 2.: Representative gross finding of uterine and mesenteric smooth muscle tumors. A Mesenteric implant tumor. B Cornish smooth muscle tumor located on the mesenteric surface. C The largest uterine leiomyoma observed during surgery. D Cross-sectional image of uterine leiomyoma.Discussion DPL is a rare, benign smooth muscle tumor characterized by multiple leiomyoma-like nodules distributed throughout the peritoneal cavity. DPL occurring during pregnancy is exceedingly uncommon, few cases were reported to date. Most patients remain asymptomatic, and the condition is frequently identified incidentally during cesarean delivery. Radiologic findings may mimic peritoneal malignancy, posing significant diagnostic and management challenges within the obstetric setting. When multiple peritoneal nodules are encountered during pregnancy, the primary differential diagnoses include parasitic leiomyoma, benign metastasizing leiomyoma, and intravenous leiomyomatosis (Supplementary Table 1, https://links.lww.com/MFM/A134). From an obstetric and gynecologic perspective, DPL is considered a benign condition. However, a malignant transformation rate of approximately 2% to 5% has been reported, and sustained remission without recurrence is uncommon in patients managed conservatively without a hysterectomy. Therefore, individualized management focusing on maternal–fetal safety, careful perioperative assessment, and postpartum radiologic surveillance is recommended when DPL is incidentally identified during pregnancy. Conclusion This report documents a case of DPL during pregnancy and summarizes relevant clinical and management features, contributing valuable observational data to the limited existing literature. Interpretation of these findings is constrained by the single-case design and the absence of standardized diagnostic or management guidelines. We hope these findings provide a practical reference for the clinical management of DPL in pregnancy, pending the development of standardized, evidence-based guidelines. Funding None. Author Contributions Z.W. conceived the case report and provided supervision. T.P. and Y.L. performed the surgery and were responsible for the clinical management of the patient. C.D. drafted the manuscript. D.W. critically revised the manuscript for important intellectual content. All authors have read and approved the final manuscript. Conflicts of Interest The authors declare no conflicts of interest. Data Availability The data that support the findings of this study are available from the corresponding author upon reasonable request. Editor Note Zilian Wang is one of the editorial board members of Maternal-Fetal Medicine. This article was subject to the journal’s standard procedures, with peer review handled independently of this editor and the associated research group.
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