Fertility-sparing surgery for a patient with a pre-operative suspected diagnosis of a Uterine Smooth Muscle Tumor of Uncertain Malignant Potential (STUMP): A case report

The patient was a 34-year-old female gravida 0 who initially presented for a fertility evaluation. She had a history of interstitial cystitis, uterine fibroids and chronic pelvic pain. She reported regular menstrual cycles every 30 days with 7–8 days of flow and associated pain. She also had a history of a right ovarian dermoid cyst with subsequent right ovarian cystectomy via Pfannenstiel. Her family history was significant for breast cancer in her paternal grandmother and father's sister, pancreatic and lung cancer in her maternal grandfather and endometriosis in her sister. She was interested in fertility preservation for personal reasons, and presented to the reproduction, endocrinology, and infertility clinic for an initial consultation of oocyte preservation. She was referred to the minimally invasive gynecologic surgery team for evaluation and management of a 4 cm posterior cervical submucosal fibroid and recurrent ovarian cyst identified on transvaginal ultrasound as part of her fertility work up. The patient was initially counseled on minimally invasive myomectomy to treat her fibroid, but due to strong desire for future vaginal delivery, she declined this more invasive procedure as cesarean section would be needed for future delivery. She underwent hysteroscopic partial resection of her fibroid and laparoscopic right ovarian cystectomy. The initial pathology reported fragments of submucosal tumor with diffuse and marked cytologic atypia, but necrosis was not seen ( Fig. 1 A). Additionally, there were foci of increased mitotic activity up to 5/10HPF ( Fig. 1 B). Smooth muscle differentiation was noted and supported by desmin and caldesmon positivity. While HMB45 and Melan A were negative, staining for MITF1 and Catepsin K raised the possibility of a perivascular epithelioid cell tumor (PEComa). Ultimately, the differential diagnosis included STUMP, PEComa, or symplastic leiomyoma. Fig. 1 Hematoxylin and eosin slides of representative samples from biopsy and resection specimens. (A) Hysteroscopic biopsy specimen with concern for STUMP. (B) Hysteroscopic biopsy specimen with mitotic figures visible, concerning for STUMP. (C) Resection specimen consistent with symplastic fibroid. (D) Resection specimen consistent with symplastic fibroid, high power field. Fig. 1 Hematoxylin and eosin slides of representative samples from biopsy and resection specimens. (A) Hysteroscopic biopsy specimen with concern for STUMP. (B) Hysteroscopic biopsy specimen with mitotic figures visible, concerning for STUMP. (C) Resection specimen consistent with symplastic fibroid. (D) Resection specimen consistent with symplastic fibroid, high power field. Given these findings, gynecologic oncology was consulted. MRI with contrast characterized a FIGO type II-V submucosal lesion in the lower posterior uterine body measuring 3.4 × 3.1 × 3.2 cm with signal extending to the subserosal surface consistent with the presumed lesion ( Fig. 2 A). Whole body PET CT did not demonstrate abnormal FDG uptake in the uterine lesion and there was no evidence of nodal or distant disease ( Fig. 2 B). Fig. 2 Pre- and post-operative imaging. (A) Pre-operative MRI (after hysteroscopic sampling) showing 3.4 × 3.1 × 3.2 cm lower uterine segment submucosal mass with T2 hypointense signal extending into subserosal surface. (B) Pre-operative PET/CT without abnormal FGD update. (C) Post-operative MRI with post-surgical changes and no new or suspicious uterine lesions. Fig. 2 Pre- and post-operative imaging. (A) Pre-operative MRI (after hysteroscopic sampling) showing 3.4 × 3.1 × 3.2 cm lower uterine segment submucosal mass with T2 hypointense signal extending into subserosal surface. (B) Pre-operative PET/CT without abnormal FGD update. (C) Post-operative MRI with post-surgical changes and no new or suspicious uterine lesions. After these results, the patient initially pursued mature oocyte cryopreservation, but due to low response, she elected to stop and proceed with resection of the lesion. Due to the size and location, a hysteroscopic resection would have been inadequate. Counseling about this rare tumor clarified the uncertain behavior of the tumor and detailed the risks and benefits of proceeding with myomectomy versus hysterectomy. Specifically, fertility options and possible oncologic risks were discussed, as well as treatment options in the case of definitive malignancy. Given the uncertainty, it was reasonable to proceed with myomectomy with a future option for hysterectomy. A shared decision was made between the patient and care team to undergo an open myomectomy with minimal disruption of the mass to preserve her fertility, minimize risks through avoiding morcellation, provide more tissue for diagnostic assessment, and remove the lesion. The case was completed through a six cm Pfannenstiel incision. The uterus was small and anteverted. An approximately 3.5 cm posterior lower uterine segment FIGO Type V fibroid was visualized. Through a hysterotomy measuring approximately 4 cm, the mass was removed with minimal disruption ( Fig. 3 ). The patient tolerated the procedure well. Final pathology showed a smooth muscle neoplasm with diffuse bizarre cytologic atypia, rare mitotic figures (up to 3/10 HPF counted on multiple slides), and no necrosis. On immunohistochemistry, HMB45 showed rare single positive cells, while Melan A was negative. Overall, these findings were consistent with a symplastic leiomyoma, also known as leiomyoma with bizarre nuclei (LBN), a benign diagnosis ( Fig. 1 C,D). Follow-up MRI after the procedure demonstrated nonspecific heterogeneity and scar in the myomectomy bed, with no new or suspicious uterine lesions ( Fig. 2 C). The patient was instructed to return to clinic in six months for an additional follow-up MRI and to discuss fertility planning. Fig. 3 Intra-operative pictures. (A) Uterus exposed through 6 cm Pfannenstiel incision. (B) Myomectomy with minimization of capsule disruption. (C) Specimen. Fig. 3 Intra-operative pictures. (A) Uterus exposed through 6 cm Pfannenstiel incision. (B) Myomectomy with minimization of capsule disruption. (C) Specimen.

Matthew P. Kipp: Writing – original draft, Investigation. Zoe A. Roecker: Writing – original draft, Investigation, Conceptualization. Azin Mashayekhi: Writing – original draft, Investigation. Jennifer M. Scalici: Writing – review & editing, Investigation. Laura C. Ramirez-Caban: Writing – review & editing, Supervision, Investigation, Conceptualization.

Written informed consent to take part in the study and to publish the article has been obtained from all participants or their legal representatives. The privacy rights of participants have been observed. This study was performed in compliance with relevant laws, regulatory frameworks and guidelines where the research took place. Ethics committee approval was not required under relevant laws and institutional guidelines. IRB approval is not required for case reports at our institution. The patient provided written informed consent for publishing this report and associated images. This research follows the CARE guidelines and the CARE checklist.

STUMP is a rare uterine tumor with recommended hysterectomy and surveillance for recurrence. In patients desiring future fertility, myomectomy without morcellation and continued surveillance can be considered as an alternate treatment option after thorough discussion regarding risks and benefits.

STUMPs remain difficult to identify pre-and post-operatively due to overlapping symptoms with both benign and malignant uterine lesions, and definitive diagnosis requiring histopathology. Imaging techniques like MRI and ultrasound have not proven diagnostic, and molecular markers can only aid in risk stratification ( Gadducci and Zannoni, 2019 ; Travaglino et al., 2021a ). A tissue sample is necessary for diagnosis, which results in nearly all STUMP diagnoses occurring after complete resection of the lesion either via myomectomy or hysterectomy. However, in this case, the tumor was concerning for STUMP prior to excision as the patient underwent a hysteroscopic biopsy. This offered the unique opportunity for shared decision making with the patient regarding treatment options which would maintain her fertility. NCCN guidelines for uterine neoplasms with confirmed or suspected malignancy limited to the uterus are to proceed with total hysterectomy, which is a conflict for patients desiring future pregnancy ( NCCN, 2026 ). Fertility-sparing measures through myomectomy with deferred hysterectomy after pregnancy have been performed in cases of STUMP and published in the literature. A systematic review of 80 patients with uterine neoplasms who pursued fertility sparing treatments and with post-operative STUMP diagnoses found that 33 of these patients became pregnant ( Arcieri et al., 2022 ). Several studies have reported on outcomes of fertility sparing treatment for patients with STUMP diagnoses. A multicenter retrospective study found that 57.4% of patients with a prior STUMP diagnosis and who tried to conceive were successful. This study also reported a tumor recurrence rate of 21.7% ( Maggiore et al., 2025 ), which is higher than the recurrence rates of 7.3–14% reported in other studies that did not specifically pursue fertility-sparing measures ( Guntupalli et al., 2009 ; Şahin et al., 2019 ). A systematic review of STUMP cases found a recurrence rate of 19.5% regardless of treatment, with about one third of these cases recurring as malignant neoplasms, typically LMS. The study found about 60% of recurrences were local. A factor significantly associated with recurrence was unprotected morcellation. Recurrence rates have significantly decreased since 2014 when the FDA reported on the elevated risk of recurrence following morcellation ( Di Giuseppe et al., 2022 ). Maggiore et al. did report a statistically significant increased risk of recurrence in those who became pregnant ( Maggiore et al., 2025 ). The range in recurrence rates between studies may be partially attributed to the smaller sample size, tumor heterogeneity, and their rarity. These studies conclude that fertility-sparing measures are safe and successful at maintaining a patient's child-bearing ability in the setting of a STUMP tumor ( Maggiore et al., 2025 ). Another challenge is the similarity of STUMP with variants of LM. Leiomyoma with bizarre nuclei (LBN), or symplastic LM, was the final pathology in this case. LBN are distinct uterine neoplasms that share features with LM and other LM subtypes. According to 2020 WHO guidelines, a LBN is a uterine neoplasm with bizarre appearing nuclei, no tumor cell necrosis, and mitotic count <5 mitoses/10 HPF 4 . It can be challenging to distinguish LBN from LM, LMS or STUMP in a biopsy specimen. Immunohistochemistry and genetic testing have been proposed as additional diagnostic tools, but histopathology remains the standard ( Guo et al., 2022 ). The main histologic feature distinguishing LBN from STUMP is mitotic count, as the cellular atypia and lack of necrosis can be found in both. It is important to differentiate LBN from STUMP or LMS to prevent overtreatment as LBN is a benign neoplasm. A meta-analysis of 12 studies with over 400 patients found that when LBN and STUMP were analyzed together, the recurrence rate was 7.7%, but LBN alone had a recurrence rate of 1.9% ( Travaglino et al., 2021b ). The treatment recommendation for patients with LMS or STUMP is a total hysterectomy ( NCCN, 2026 ). LBN can be approached more conservatively with myomectomy, especially for those seeking to maintain fertility. For patients with a final diagnosis of STUMP, surveillance with gynecologic oncology with regular pelvic exams and imaging is recommended, regardless of management with myomectomy or hysterectomy ( Gadducci and Zannoni, 2019 ). In cases of LBN, patients must be followed closely afterward, as there is a low but reported risk of recurrence; routine imaging surveillance is not recommended ( Guo et al., 2022 ; Travaglino et al., 2021b ). STUMP tumors are rare uterine tumors with potential for recurrence and malignancy. Hysterectomy is recommended given the risk of malignant transformation, but fertility sparing management may be safe, although is not the standard of care. In our report, a pre-operative concern for STUMP tumor led to a detailed discussion and shared decision making with the patient, and she ultimately elected an abdominal myomectomy. Although the standard recommended management is to proceed with hysterectomy, in the case of a strong desire for future fertility, a uterine sparing approach can be considered in patients with a preemptive diagnosis of STUMP with thorough counseling. Ultimately, final pathology was consistent with leiomyoma with bizarre nuclei, which shares histologic features with STUMP but has a low risk of recurrence and is considered a benign lesion. This case report underscores the importance of weighing risks and benefits for each individual, especially when there is diagnostic uncertainty and hysterectomy irrevocably precludes future pregnancy.

Uterine smooth muscle tumors of uncertain malignant potential (STUMPs) are rare and heterogeneous tumors that are histologically distinct from benign leiomyoma (LM) or malignant leiomyosarcoma (LMS). Common presenting symptoms for patients with STUMP are pelvic pain, dysmenorrhea, abnormal uterine bleeding, and dysuria, which are symptoms common in both benign and malignant uterine lesions ( Tinelli et al., 2023 ). Most diagnoses occur in perimenopausal women, but have been reported to occur in a range of 20–85 years ( Bell et al., 1994 ; Female Genital Tumours, 2020 ). Bell et al suggested identifying smooth muscle tumors of the uterus as LM or LMS based on histological features of cellular atypia, tumor cell necrosis and mitotic count ( Bell et al., 1994 ). This study defined LMS by the presence of at least two of the following: significant cytologic atypia, tumor cell necrosis, ≥10 mitoses per 10 high-power fields. In contrast, LM have only mild atypia, no tumor cell necrosis, and ≤4 mitoses per 10 high-power fields ( Bell et al., 1994 ; Guntupalli et al., 2009 ). LMS can be further categorized as conventional (spindle cell), myxoid, or epithelioid based on histological features ( Female Genital Tumours, 2020 ). STUMP was added as an official diagnosis by the WHO in 2014 due to its unique histological presentation, which does not fit the criteria for LM or LMS ( Kurman, 2014 ). A STUMP diagnosis is challenging due to significant histologic heterogeneity among lesions and lack of a standardized set of diagnostic parameters ( Gadducci and Zannoni, 2019 ). There is still no universally agreed upon definition, but 2020 WHO guidelines define STUMP by the following histologic criteria ( Female Genital Tumours, 2020 ): 1. Focal/multifocal or diffuse nuclear atypia, no tumor cell necrosis, with 5–9 mitoses/10 HPF 2. Tumor cell necrosis alone, but no other worrisome features 3. No cytological atypia, no tumor cell necrosis, with >15 mitoses/10 HPF 4. Tumors with diffuse nuclear atypia and uncertain mitotic counts, often due to brisk prominent karyorrhexis Focal/multifocal or diffuse nuclear atypia, no tumor cell necrosis, with 5–9 mitoses/10 HPF Tumor cell necrosis alone, but no other worrisome features No cytological atypia, no tumor cell necrosis, with >15 mitoses/10 HPF Tumors with diffuse nuclear atypia and uncertain mitotic counts, often due to brisk prominent karyorrhexis Pre-operative identification is difficult as definitive diagnosis requires histological confirmation which most often follows surgical resection. Molecular and genetic markers such as p53, p16 and ki67 have been proposed as features to aid in diagnosis ( Travaglino et al., 2021a ). While molecular markers may lend support to the identity or prognosis of a particular uterine lesion, histology is necessary for diagnosis ( Chiang, 2023 ; Travaglino et al., 2021a ). The National Comprehensive Cancer Network (NCCN) guidelines for uterine neoplasms limited to the uterus with known or suspected malignancy are to undergo total hysterectomy (TH) en bloc resection with or without bilateral salpingoophorectomy (BSO), with avoidance of morcellation ( NCCN, 2026 ). There are no NCCN guidelines specifically for STUMP tumors, but due to their malignant potential, hysterectomy is preferred ( Travaglino et al., 2021a ). STUMP tumors have been reported to recur in about 19.5% of cases. About one third of the recurrences are malignant, most commonly leiomyosarcoma. This risk of malignant transformation informs the decision to pursue a hysterectomy ( Di Giuseppe et al., 2022 ). Myomectomy has been reported as a potential fertility-sparing option for STUMPs based on several case series reporting myomectomies which were subsequently diagnosed as STUMP tumors on post-operative pathology. In contrast, this case report presents a patient with a concern for STUMP diagnosis on pathology after initial hysteroscopic myomectomy who chose to pursue fertility-sparing care through an abdominal myomectomy with avoidance of morcellation. This case demonstrates the challenges of pursuing definitive treatment for a potentially malignant uterine lesion that conflicts with a patient's reproductive goals, particularly when the diagnosis is uncertain.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.