A Large Pedunculated Subserosal Leiomyoma Masquerading as a Pelvic Tumor in Early Pregnancy: A Rare Case Report

ABSTRACT

Uterine leiomyomas, commonly known as fibroids, are the most prevalent pelvic tumors in females, affecting 20%–30% of women of reproductive age. However, large pedunculated subserosal leiomyomas presenting during early pregnancy are uncommon and may mimic adnexal or intra‐abdominal malignancies, posing diagnostic and management challenges. This case presents a rare example of a large pedunculated subserosal leiomyoma in early pregnancy masquerading as a pelvic tumor. This report highlights the diagnostic challenge, intraoperative findings, and successful maternal outcome following timely surgical management. Here we present a case of a 31‐year‐old G3 P0 + 2 L0 woman who presented to our specialty hospital in Northern Tanzania at 11 weeks and 5 days gestational age (GA). She has a history of progressive abdominal distension for 1 year, associated with abdominal pain, vomiting, nausea, and early satiety. Initial abdominal ultrasound evaluation revealed a viable intrauterine pregnancy and a large heterogeneous abdominal mass with increased vascularity on Doppler ultrasound. Magnetic resonance imaging (MRI) identified a 21 × 10 × 15 cm, well‐defined encapsulated mass extending intraperitoneally, abutting major abdominal vessels, consistent with a pelvic tumor. Explorative laparotomy revealed this mass to be a pedunculated subserosal fibroid arising from the uterine fundus through a narrow vascular stalk. Myomectomy was successfully performed with minimal blood loss and histopathological examination confirmed a benign leiomyoma with cystic degeneration. The postoperative course was uneventful. Subsequent follow‐up at 25 weeks GA showed a viable intrauterine pregnancy with normal fetal growth.

Key Clinical Message

This rare case emphasizes the importance of recognizing large pedunculated subserosal leiomyomas as potential mimickers of pelvic or adnexal tumors in pregnancy. Comprehensive imaging assessment and multidisciplinary management are essential for accurate diagnosis and safe surgical planning. With careful intraoperative and postoperative monitoring, myomectomy for a subserosal myoma during pregnancy can be safely performed, preserving both maternal health and fetal viability.

1. Introduction

Uterine leiomyomas are the most common benign smooth muscle tumors of the uterus, affecting approximately 20%–40% of women of reproductive age and up to 10% of pregnancies depending on diagnostic methods [1, 2]. Their growth is estrogen and progesterone dependent. While most remain asymptomatic, a subset may cause pain, menorrhagia, infertility, or obstetric complications such as miscarriage, malpresentation, preterm labor, or postpartum hemorrhage [3, 4].

Among the subtypes, pedunculated subserosal leiomyomas are uncommon, but clinically important. They project from the uterine surface via a narrow stalk and can grow to considerable size, sometimes occupying the pelvic cavity and mimicking adnexal or other pelvic tumors [1, 2, 3, 4, 5]. Large pedunculated subserosal fibroids may undergo torsion, infarction, or red degeneration, presenting with signs of acute abdomen. They are often mistaken for ovarian torsion, tubo‐ovarian mass, or malignancy [6, 7]. Such lesions can be difficult to distinguish sonographically from ovarian masses, particularly in early pregnancy when the uterus is still confined to the pelvis [8].

Diagnosis of huge pedunculated subserosal leiomyoma in pregnancy can be challenging especially through ultrasonography, even though ultrasonography is the first‐line imaging modality. This is due to the distorted pelvic anatomy caused by the gravid uterus and limited acoustic window during pregnancy, making differentiation from ovarian neoplasms difficult [6, 7, 8]. Magnetic resonance imaging (MRI) can be helpful when the diagnosis remains uncertain, providing better delineation of the uterine origin of the mass [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13].

Management of leiomyomas during pregnancy remains controversial. Conservative management is preferred unless there are complications such as torsion, large size, intractable pain, or diagnostic uncertainty regarding malignancy [2, 3, 4, 5, 6, 7, 8, 9]. Myomectomy during pregnancy is generally avoided due to concerns about hemorrhage, pregnancy loss, or preterm labor. However, emerging evidence suggests that when performed in carefully selected cases and by experienced surgeons, antepartum myomectomy, especially for pedunculated subserosal fibroids, can be safe and associated with favorable maternal and fetal outcomes [3, 4, 5, 6, 7, 8, 9, 10].

The rarity of this case lies in its occurrence during early pregnancy and its unusual clinical presentation as a pelvic tumor, rather than a typical uterine mass. Most reported cases of pedunculated subserosal fibroids occur in the second or third trimester or are detected incidentally during cesarean delivery [11, 12]. Presentation in the first trimester with a mass of more than 20 cm, mimicking a pelvic tumor, is exceptionally rare. We therefore present this rare case of a large pedunculated subserosal leiomyoma in early pregnancy, masquerading clinically and radiologically as a pelvic tumor from Northern Tanzania in a woman with two prior ectopic pregnancies.

2. Case History

A 31‐year‐old woman, G3 P0 + 2 L0, presented to our specialty hospital in Northern Tanzania at 11 weeks and 5 days of GA with a one‐year history of progressive abdominal distension associated with abdominal pain, easy fatigability, nausea, vomiting, and early satiety. The abdominal pain was generalized over the entire abdomen, dull in nature, gradual onset, and progressively worsened over time. She denied any history of lower limb swelling, weight loss, constipation, or change in bowel function. She reached menarche at the age of 15 years, reported to have heavy menstrual bleeding lasting 8 days and requiring approximately five pads per day, fully soaked. There was no documented history of gynecological imaging, hormonal therapy, or surgical interventions before pregnancy. She had not received any prior treatment for her menstrual symptoms. Her obstetric history included two previous ectopic pregnancies: the first being a right tubal ectopic pregnancy in 2019 and the second a right ovarian ectopic pregnancy in 2022, for which she underwent laparoscopic salpingectomy and oophorectomy, respectively. Her past medical history was unremarkable, and she reported no history of alcohol use or smoking. There was no personal or family history of ovarian, cervical, or breast cancer.

On physical examination, the patient was visibly uncomfortable, but alert and oriented with a Glasgow Coma Scale score of 15. Vital signs were stable, with a normal blood pressure of 128/70 mmHg, a pulse of 68 beats per minute, and a respiratory rate of 16 breaths per minute. Lower limb pitting edema was not present. Abdominal examination revealed generalized marked distension of the abdomen correlating to a fundal height of 26 cm, with no rigidity or hepatosplenomegaly. There was tenderness in the right and left lower quadrant and a palpable smooth, firm mass in the pelvis. Bowel sounds were not clearly audible. On vaginal examination, there were no visible abnormalities of the cervix. The examination of other systems was unremarkable.

3. Investigations and Management

The acute onset of severe abdominal pain in the presence of a large abdominopelvic mass guided the differential diagnosis toward gynecologic causes of an acute abdomen. An adnexal mass with possible torsion was considered due to the sudden pain and pelvic origin of the mass. Uterine leiomyoma was included in the differential based on the history of heavy menstrual bleeding and a firm pelvic mass on examination. Non‐gynecologic causes were considered less likely due to the absence of gastrointestinal or urinary symptoms. Upon investigation, her cancer antigen 125 (CA‐125) was 40 U/mL (reference range: 0.00–35.00 U/mL) and carcinoembryonic antigen (CEA) was 6 U/mL (reference range: 0.00–5.093 U/mL), indicating mild elevation of tumor markers. She had a positive urine pregnancy test and the complete blood count, liver and renal function tests all were within normal limits. Cardiac investigations including an ECG and ECHO were also normal. Abdominal ultrasound demonstrated a large, mobile, heterogeneous intra‐abdominal mass with high vascularity on color Doppler imaging, appearing to arise from the right adnexa. The left ovary appeared normal. A single live intrauterine fetus was noted, with a crown‐rump length (CRL) of 4.80 cm corresponding to a GA of 11 weeks and 3 days (Figure 1A,B). Subsequent MRI revealed a well‐defined, encapsulated soft tissue mass measuring approximately 21 × 10 × 15 cm located within the intraperitoneal cavity extending extraperitoneally (Figure 2A–C).

FIGURE 1.

(A) Sagittal abdominal ultrasound view revealed a large, mobile heterogeneous intrabdominal mass was seen. The fibroid appears as a well‐defined, hypoechoic (darker) mass arising from the perimetrium, causing distortion of the normal uterine contour. (B) A single live intrauterine fetus at an approximate gestational age of 11 weeks and 3 days. The measurement indicates a Crown‐Rump Length (CRL) of 4.80 cm, corresponding to a Gestational Age (GA) of 11 weeks and 3 days (11w3d).

FIGURE 2.

(A) Coronal T2‐ weighted MRI view (B) Sagittal T2‐weighted MRI view (attached to the uterus by a thin stalk (peduncle) arising from the uterine fundus) and (C) Axial T2‐weighted MRI view revealed a huge mass measuring 21 × 10 × 15 cm sized well‐defined encapsulated intrabdominal soft tissue mass seen in the intraperitoneal cavity extending extraperitoneally, abutting the right kidney, abdominal aorta, and effacing the IVC, displacing the large bowel loops peripherally. The lesion abuts and pushes the left abdominal wall muscles anteriorly. The mass shows mixed signal intensity, suggestive of red (hemorrhagic) or cystic degeneration, a common finding in fibroids during pregnancy.

The mass was abutting the right kidney, abdominal aorta, and inferior vena cava (IVC), with peripheral displacement of the large bowel loops. It also met and displaced the left abdominal wall muscles anteriorly. The lesion exhibited heterogeneous, low signal intensity with intralesional cystic changes and restricted diffusion on ADC/DWI mapping, suggesting high cellularity. No para‐aortic lymphadenopathy was noted. A gravid uterus was identified, with focal abutment of the lesion on the left aspect of the uterine fundus. No adnexal involvement was observed; the left ovary appeared normal, whereas the right ovary was not clearly visualized. The overall radiologic impression favored a pelvic tumor.

The patient was prepared for an explorative laparotomy under general anesthesia, positioned in a left lateral tilt. The abdomen was opened in layers with an extended umbilical midline incision. A well‐circumscribed, lobulated, pedunculated subserosal fibroid was noted arising from the uterine fundus through a narrow vascular stalk, not appearing to be twisted. The mass measured approximately 21 × 10 × 15 cm, had a smooth congested surface with prominent superficial vessels, and was freely mobile within the abdominal cavity without adhesions to surrounding structures (Figure 3A). The gravid uterus was intact and appeared normal apart from the fibroid attachment site. There was no obvious solid component to the mass, and minimal ascitic fluid was present. The ovaries and fallopian tubes were grossly normal. The pedunculated fibroid was carefully isolated, its stalk clamped, ligated, and excised with minimal blood loss (Figure 3B). Estimated blood loss was approximately 80 mL with a total operative time of 60 min. The uterine surface was inspected and noted to have achieved hemostasis, confirming successful myomectomy. The specimen was submitted for histopathological evaluation (Figure 3C).

FIGURE 3.

(A) A huge pedunculated subserosal uterine fibroid arising from the fundus of the uterus through a narrow stalk (pedicle) measuring 21 × 10 × 15 cm was identified. The mass is well‐circumscribed, lobulated, and has a smooth, congested surface with visible engorged vessels. (B) After partial mobilization, the gravid uterus is visualized beneath the fibroid. The uterus appears intact, confirming no invasion into the myometrium. (C) The specimen which was taken for histopathology appeared as a multinodular, encapsulated mass with a shiny serosal surface and prominent vascular markings.

4. Results

The patient was managed on the gynecology ward with an uneventful post‐operative course. She received analgesia, antibiotics, intravenous fluid support, and thromboprophylaxis. Histopathological examination of the excised specimen revealed a single, encapsulated mass measuring 21 × 10 × 15 cm. On gross examination, the cut surface displayed a characteristic white, whorled appearance with a central area of necrosis and a cystic space measuring 6 × 4 cm containing yellow, clear fluid. Microscopically, the lesion was well‐circumscribed and composed of bland spindle‐shaped smooth muscle cells arranged in interlacing fascicles, with areas of central cystic degeneration evident. These histological features were consistent with a diagnosis of leiomyoma (Figure 4).

FIGURE 4.

Histopathology showing a well‐circumscribed leiomyoma composed of bland spindle‐shaped smooth muscle cells arranged in interlacing fascicles. (A) Low‐power view (H&E × 4). (B) Intermediate‐power view (H&E × 10) demonstrating spindle cells with cigar‐shaped nuclei and no cytological atypia.

The patient recovered well postoperatively and was discharged on the third postoperative day. An obstetric review prior to discharge, including an ultrasound examination, confirmed a viable intrauterine pregnancy with reassuring fetal cardiac activity. She was counseled regarding the potential risk of fibroid recurrence and the implications for future fertility. At her follow‐up visit 2 weeks later, she remained stable. A subsequent ultrasound performed at 25 weeks of gestation confirmed a viable intrauterine pregnancy with normal fetal growth and no complications.

5. Discussion

In this case we discuss the diagnostic challenges, management of a complicated pregnancy, and implications for complex reproductive counseling. Our patient is a great example for demonstrating the necessary steps and tools required for a favorable outcome.

In Sub‐Saharan Africa, the burden of uterine fibroids is disproportionately high due to genetic predisposition and environmental factors [13], however, literature on atypical fibroid presentations in pregnancy is notably limited. A recent case report from Nigeria described a large subserosal fibroid misdiagnosed as an ovarian tumor in a non‐pregnant woman, highlighting similar diagnostic challenges and the need for advanced imaging modalities in resource‐constrained settings [14]. Our case, originating from Northern Tanzania, adds to this scarce body of evidence and underscores the importance of recognition and multidisciplinary management in such complex scenarios.

While often asymptomatic, the leiomyoma in our patient caused abdominal distension and discomfort early in pregnancy. These features are consistent with prior reports including one from Costa and Cunha describing a torsed pedunculated fibroid presenting with acute pain mimicking adnexal torsion [2]. Bubmann et al. reported that symptomatic fibroids often present with pain, pressure, or rapid enlargement necessitating intervention [3]. Helmi et al. reported a similar case where a pregnant patient had a large subserosal leiomyoma adhered to the omentum and bowel, complicating the surgical procedure [15]. The combination of early gestational age and unusually large size in our case adds to its rarity.

Tumor markers such as CA‐125 and CEA were mildly elevated in our patient, raising initial concern for malignancy. However, these markers are nonspecific and can be elevated in benign conditions such as fibroids, endometriosis, and pregnancy itself. ESGO/INCIP guidelines caution against over‐reliance on tumor markers in pregnant patients and recommend integrating clinical, radiologic, and surgical findings for accurate diagnosis [16]. CA‐125 levels are less frequently elevated in benign gynecologic conditions compared to malignancies, but overlap exists, necessitating careful interpretation [17].

Imaging evaluation remains challenging in early pregnancy. Ultrasound may misclassify large exophytic fibroids as adnexal or pelvic tumors, especially when the stalk is thin and the uterus small [7]. ACOG recommends MRI as a second‐line imaging tool when ultrasound findings are inconclusive, especially in pregnant patients where radiation exposure must be avoided [18]. MRI is considered superior for differentiating fibroids versus tumors, confirming uterine origin, identifying bridging vessels or pedicles, and evaluating degeneration, without radiation exposure [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]. In this case, MRI demonstrated a large heterogeneous mass with intralesional cystic changes and restricted diffusion on ADC/DWI mapping. Although restricted diffusion raised concern for high cellularity and a possible malignant process, this finding is not specific and can also be observed in benign conditions such as cellular or degenerating leiomyomas. Given the mass's large size (21 × 10 × 15 cm), significant compressive effects on bowel, vessels, and gravid uterus, and risks of obstruction, preterm labor, or acute decompensation with advancing gestation, surgical exploration via laparotomy was justified for definitive histopathologic diagnosis and potential therapeutic resection, prioritizing maternal‐fetal safety in a multidisciplinary approach.

Management of symptomatic fibroids in pregnancy requires individualized assessment, balancing maternal and fetal risks. ACOG recommends surgical intervention only for clearly symptomatic lesions or those causing complications, with obstetric consultation and close intra‐ and post‐operative monitoring [18]. ESGO/INCIP guidelines advocate multidisciplinary evaluation for pelvic masses to rule out malignancy prior to intervention [16]. Myomectomy can be performed during any trimester of pregnancy. The type of surgery should be individualized depending on the duration of pregnancy, location, type, and size of the fibroid, and other maternal factors. In our patient, the large, symptomatic, and diagnostically uncertain mass warranted antepartum myomectomy, consistent with these recommendations.

Fetal outcomes in antepartum myomectomy are generally favorable with careful selection and monitoring. In our patient, pregnancy continued uneventfully postoperatively, with serial ultrasounds confirming fetal viability and no immediate complications such as preterm labor or growth restriction. This aligns with reports documenting live births after surgical removal of large pedunculated fibroids during pregnancy [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]. Our patient's favorable outcome illustrates that surgical intervention in carefully selected cases can be safe and effective, even in early pregnancy, when multidisciplinary planning and guideline‐directed management are applied.

Regarding future pregnancies, preserving uterine integrity and minimizing intraoperative trauma are critical to maintaining reproductive potential. Literature suggests that removal of pedunculated fibroids, when the cavity is intact and adhesions are minimized, does not significantly impair fertility [2]. Lee et al. advise close monitoring of uterine integrity and fetal growth in women with prior myomectomy [21]. In our patient, careful surgical technique and postoperative recovery are expected to support subsequent gestations. The history of prior ectopic pregnancies, however, may continue to influence fertility and warrants preconception counseling and close prenatal care. Reporting such cases contributes to the limited evidence on long‐term reproductive outcomes following antepartum myomectomy.

Recurrence of fibroids is a known concern, with rates ranging from 15% to 30% within 5 years post‐myomectomy [22]. Factors influencing recurrence include age, number of fibroids removed, and residual tissue. ACOG recommends counseling patients on recurrence risk and discussing fertility‐preserving options such as hormonal therapy or uterine artery embolization in non‐pregnant patients [18]. Our patient was appropriately counseled on these risks and remains under obstetric surveillance.

6. Conclusion

Large pedunculated subserosal leiomyomas in early pregnancy are rare and can mimic pelvic tumors, particularly in patients with prior ectopic pregnancies. Accurate diagnosis requires careful imaging interpretation, with MRI providing detailed anatomical information. Symptomatic or uncertain masses may necessitate antepartum myomectomy, which can be safely performed with multidisciplinary planning and guideline‐directed care. Successful maternal and fetal outcomes, as observed in this case, underscore the importance of individualized management, preoperative evaluation, and postoperative monitoring. A key limitation in this case was the absence of detailed intraoperative documentation from the patient's two prior laparoscopic surgeries (salpingectomy and ovariotomy). The patient was referred to our facility without clear records of intraoperative findings, such as the presence of fibroids, adhesions, or other pelvic pathology at those procedures. This is a common challenge in referral settings and highlights the need for improved documentation and communication between healthcare facilities to enhance diagnostic accuracy and surgical planning in similar complex cases. Reporting such rare presentations enhances awareness and guides clinicians in managing complex early gestational fibroids while preserving future reproductive potential.

Author Contributions

John Lugata: conceptualization, data curation, formal analysis, investigation, methodology, resources, validation, visualization, writing – original draft, writing – review and editing. Felix Luginga: conceptualization, data curation, investigation, methodology, resources, writing – original draft, writing – review and editing. Tecla Lyamuya: conceptualization, data curation, formal analysis, investigation, methodology, supervision, validation, writing – original draft, writing – review and editing. Glory Maringo: conceptualization, data curation, formal analysis, investigation, methodology, resources, supervision, validation, visualization, writing – original draft, writing – review and editing. Eusebious Maro: data curation, formal analysis, investigation, methodology, resources, supervision, validation, visualization, writing – original draft, writing – review and editing. Alex Mremi: conceptualization, data curation, formal analysis, investigation, resources, supervision, validation, visualization, writing – original draft, writing – review and editing. Bariki Mchome: conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, resources, supervision, validation, visualization, writing – original draft, writing – review and editing.

Funding

The authors have nothing to report.

Ethics Statement

The patient provided written informed consent to allow for her de‐identified medical information to be used in this publication. A waiver for ethical approval was obtained from the authors institution review board committee.

Consent

Written informed consent for the publication of clinical details and images was obtained from the patient. A copy of the consent is available for review by the chief editor of this journal.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

No data generated from this study.