Parasitic leiomyoma: A rare case report with imaging, surgical and histopathological correlation.

A 32-year-old unmarried female presented with lower abdominal pain, heaviness, and dysmenorrhea for 3 months. The pain was intermittent and cramping, associated with constipation and occasional nausea. She denied oral contraceptive use or family history of malignancy. She had undergone laparoscopic myomectomy 7 years prior for a large anterior intramural fibroid measuring approximately 10 × 12 cm, during which power morcellation was used for fibroid retrieval. Physical examination revealed a firm 14-week-sized mass in the hypogastrium with a well-healed surgical scar. Routine laboratory tests were normal except for mildly elevated CA-125 (52 U/mL) and CA 19-9 (46 U/mL), while AFP and β-hCG were within normal limits. Initial transabdominal ultrasound revealed a large heterogeneous hypoechoic uterine mass consistent with a fibroid and multiple smaller well-defined hypoechoic lesions along the anterior abdominal wall, raising suspicion of postoperative implantation. MRI was performed for further characterization. Contrast-enhanced MRI (CE-MRI) of the abdomen and pelvis showed a well-defined multilobulated T2-heterogeneously hypointense and T1-isointense lesion in the uterine fundus (measuring approximately 9.3 × 8.5 × 9.6 cm) showing avid heterogeneous postcontrast enhancement and patchy diffusion restriction ( Figs. 1 , and 2 ). Multiple additional T2-heterogeneously hypointense, T1-isointense lesions were seen along the posterior margin of the left rectus abdominis muscle, the largest measuring approximately 4.6 × 3.6 cm ( Figs. 1 , and 2 ). The lesions exhibited signal characteristics similar to uterine fibroids, with avid postcontrast enhancement and no necrosis or blooming. These were consistent with parasitic leiomyomas along the previous laparoscopic port site. A right ovarian cyst (∼3.4 cm) demonstrated T1 hyperintensity with T2 shading sign, consistent with an endometriotic cyst, displacing ovarian parenchyma anterolaterally ( Fig. 3 ). Fig. 1 (A) Axial T1-weighted, (B) Axial T1 fat-saturated, and (C) Axial T2-weighted images show a well-defined T1 isointense and T2 hyperintense lesion along the posterior margin of the left rectus abdominis muscle (thin white arrow), consistent with a parasitic leiomyoma. A larger multilobulated uterine fundal fibroid appears T1 hypointense and heterogeneously T2 hyperintense (broad arrow). (D) Sagittal T2-weighted image demonstrates multiple similar lesions posterior to the rectus sheath (white arrows) along with the uterine fibroid. Fig 1: Fig. 2 Diffusion-weighted and postcontrast MRI images of the same patient. (A) Diffusion-weighted image and (B) corresponding ADC map show patchy diffusion restriction in both the parasitic lesion (broad arrow) and uterine fibroid (thin arrow). (B) (C) Postcontrast T1-weighted image demonstrates heterogeneous enhancement in both lesions. Fig 2: Fig. 3 (A)Axial T1 weighted and (B) Axial T2 fat saturated weighted images showing a well defined T1 hyperintense and T2 heterogeneously hypointense lesion with T2 shading sign in the right adnexa (marked by white arrows)- suggestive of Endometriotic cyst. Fig 3: (A) Axial T1-weighted, (B) Axial T1 fat-saturated, and (C) Axial T2-weighted images show a well-defined T1 isointense and T2 hyperintense lesion along the posterior margin of the left rectus abdominis muscle (thin white arrow), consistent with a parasitic leiomyoma. A larger multilobulated uterine fundal fibroid appears T1 hypointense and heterogeneously T2 hyperintense (broad arrow). (D) Sagittal T2-weighted image demonstrates multiple similar lesions posterior to the rectus sheath (white arrows) along with the uterine fibroid. Diffusion-weighted and postcontrast MRI images of the same patient. (A) Diffusion-weighted image and (B) corresponding ADC map show patchy diffusion restriction in both the parasitic lesion (broad arrow) and uterine fibroid (thin arrow). (B) (C) Postcontrast T1-weighted image demonstrates heterogeneous enhancement in both lesions. (A)Axial T1 weighted and (B) Axial T2 fat saturated weighted images showing a well defined T1 hyperintense and T2 heterogeneously hypointense lesion with T2 shading sign in the right adnexa (marked by white arrows)- suggestive of Endometriotic cyst. The patient underwent open myomectomy, excision of peritoneal nodules, and right ovarian cystectomy under general anaesthesia. Multiple firm nodular lesions were noted on the pelvic peritoneum and along the rectus sheath ( Fig. 4 ). All were completely excised . Fig. 4 Intraoperative findings (A) Intraoperative image demonstrating a well-circumscribed parasitic leiomyoma adherent to the peritoneum, separate from the uterus, being mobilized with surgical instruments (marked by white arrow). (B,C) Operative field after mobilization, showing multiple small peritoneal nodules along the pelvic peritoneum. These were carefully dissected and excised in toto. Fig 4: Intraoperative findings (A) Intraoperative image demonstrating a well-circumscribed parasitic leiomyoma adherent to the peritoneum, separate from the uterus, being mobilized with surgical instruments (marked by white arrow). (B,C) Operative field after mobilization, showing multiple small peritoneal nodules along the pelvic peritoneum. These were carefully dissected and excised in toto. Grossly, the excised nodules were firm, grey-white with a whorled cut surface. Microscopy revealed spindle cells arranged in fascicles with eosinophilic cytoplasm and elongated cigar-shaped nuclei, consistent with leiomyoma ( Figs. 5 ). Histology of the right ovarian cyst showed endometrial glands and stroma with hemosiderin-laden macrophages ( Fig. 6 ), confirming an endometriotic cyst. The postoperative period was uneventful, and the patient remains asymptomatic at 6-month follow-up. Fig. 5 Post operative histopathological analysis of the specimen (A) Gross photograph shows multiple, well circumscribed, unencapsulated tumor nodules. Cut surface shows greyish white to tan white firm tumor with whorled appearance. (B,C) Haematoxylin and eosin (H&E) stained section shows tumor composed of spindle cells arranged in intersecting fascicles with nuclear palisading (H&E; A x40, B x100). (D, E) Higher magnification demonstrates spindle cells with indistinct borders, eosinophilic fibrillary cytoplasm, and cigar-shaped nuclei with small nucleoli (H&E; C x200,D x400). Fig 5: Fig. 6 Post operative histopathological analysis of the endometriotic cyst (A and B) Hematoxylin and eosin (H&E) stained section shows ovarian cyst wall with variable degree of inflammation and presence of endometrial glands (H&E; x40), (C) Shows presence of endometrial glands (H&E; x200), (D) Shows presence of hemosiderin laden macrophages (H&E; x200). Fig 6: Post operative histopathological analysis of the specimen (A) Gross photograph shows multiple, well circumscribed, unencapsulated tumor nodules. Cut surface shows greyish white to tan white firm tumor with whorled appearance. (B,C) Haematoxylin and eosin (H&E) stained section shows tumor composed of spindle cells arranged in intersecting fascicles with nuclear palisading (H&E; A x40, B x100). (D, E) Higher magnification demonstrates spindle cells with indistinct borders, eosinophilic fibrillary cytoplasm, and cigar-shaped nuclei with small nucleoli (H&E; C x200,D x400). Post operative histopathological analysis of the endometriotic cyst (A and B) Hematoxylin and eosin (H&E) stained section shows ovarian cyst wall with variable degree of inflammation and presence of endometrial glands (H&E; x40), (C) Shows presence of endometrial glands (H&E; x200), (D) Shows presence of hemosiderin laden macrophages (H&E; x200).

The authors confirm that written, informed consent for publication of the clinical details and images was obtained from the patient’s parents.

• Parasitic leiomyoma mimics peritoneal carcinomatosis but is benign. • A history of laparoscopic morcellation is a significant risk factor. • MRI accurately differentiates parasitic leiomyomas from malignant lesions. • Histopathology confirms the diagnosis. • Awareness avoids misdiagnosis and overtreatment. Parasitic leiomyoma mimics peritoneal carcinomatosis but is benign. A history of laparoscopic morcellation is a significant risk factor. MRI accurately differentiates parasitic leiomyomas from malignant lesions. Histopathology confirms the diagnosis. Awareness avoids misdiagnosis and overtreatment.

Ekakshi Varshney: Primary author, conceived and drafted the manuscript of case report, provided stylistic/grammatical revisions to the manuscript, collected data and review of literature on the pertaining topic, Performed real-time imaging and imaging protocols for respective modalities. Poonam Sherwani: Provided revisions to scientific content of the manuscript, proofreading the manuscript, providing administrative support, offering general supervision, approving the final submission of the paper. Nivedita Sharma: Author contributed to the reviewing the manuscript, critically revising it for important intellectual content and editing the final case report. Ravi Hari Phulware: The Author helped with data collection, imaging review, analysis. Latika Chawla: The Author helped with data collection, imaging review, analysis. Abhishek Gupta: The Author helped with data collection, critically revising it for important intellectual content and editing the final case report.

Parasitic leiomyoma should be suspected in reproductive-age women with multiple peritoneal or abdominal-wall masses and prior laparoscopic myomectomy involving morcellation. MRI provides characteristic features that help differentiate it from malignant peritoneal disease. Recognition of this benign entity prevents unnecessary investigations and aggressive therapies.

Parasitic leiomyomas are benign smooth-muscle tumors that become separated from the uterus and subsequently develop an independent blood supply at an ectopic site. Historically, they were attributed to pedunculated subserosal fibroids that lost uterine attachment. However, the contemporary understanding strongly associates them with iatrogenic dissemination following laparoscopic myomectomy, especially when power morcellation is used [ [1] , [2] , [3] ]. Small viable leiomyoma fragments may disperse into the peritoneal cavity, implant on serosal or fascial surfaces, and slowly proliferate under the influence of oestrogen and progesterone [ 4 ]. The latency period between surgery and clinical presentation typically ranges from 3 to 10 years, which often obscures the causal relationship [ 3 ]. The incidence has risen in parallel with minimally invasive gynaecologic surgery adoption, prompting recommendations for contained morcellation techniques to reduce tissue seeding [ 5 ]. Ultrasound serves as the initial modality in evaluating suspected parasitic leiomyomas. These lesions typically appear as well-defined, solid, hypoechoic masses with internal vascularity on color Doppler, similar in echotexture to uterine leiomyomas but located separately from the uterus. MRI provides superior soft-tissue characterization and is often pivotal in diagnosis. The lesions typically demonstrate T1-isointensity and T2-hypointensity with heterogeneous postcontrast enhancement, mirroring the signal characteristics of uterine leiomyomas. Importantly, parasitic leiomyomas can be seen within the peritoneal cavity, typically on the omentum and peritoneum, but also in the abdominal wall (due to direct invasion or at a laparoscopic portal), the vagina, bladder, or retroperitoneum. CT or FDG-PET/CT may show multiple soft-tissue nodules but absence of ascites, omental caking, or high FDG uptake helps distinguish parasitic leiomyomas from peritoneal carcinomatosis. This mimicry remains one of the major diagnostic challenges, and misinterpretation may lead to unnecessary oncologic workup or aggressive surgery 1. Scar Endometriosis with Peritoneal Implants: Endometriotic deposits may appear on ultrasound as irregular, heterogeneously hypoechoic nodules with internal echoes and peripheral vascularity. MRI classically demonstrates T1 hyperintense foci due to hemorrhage and T2 shading. Absence of hemorrhagic signal characteristics and lack of associated endometriotic lesions in our case argued against this diagnosis. 2. Leiomyosarcoma: On ultrasound, leiomyosarcomas often present as heterogeneous solid masses with irregular or lobulated margins, areas of cystic degeneration or necrosis, and increased, disorganized vascularity. Rapid growth and infiltrative features support malignancy. No such imaging or histopathological features were observed in our case. 3. Peritoneal Carcinomatosis: Ultrasound may reveal multiple hypoechoic peritoneal nodules, omental thickening, and ascites. PET-CT typically demonstrates increased metabolic activity, and tumor markers (eg, CA-125, CA 19-9) are often elevated. In our case, there was no ascites, PET-CT showed no abnormal uptake, and tumor markers were within normal limits. 4. Lymphadenopathy: Pelvic or para-aortic lymph nodes usually appear as oval hypoechoic nodes with an echogenic hilum, following expected nodal chains. The lesion in our case lacked nodal morphology and was pedunculated from peritoneal surfaces, making lymphadenopathy unlikely. 5. Abdominal Wall Desmoid Tumor: Desmoid tumors typically present on ultrasound as iso- to hypoechoic masses with poorly defined, infiltrative margins arising from musculoaponeurotic structures. Our lesion was well-circumscribed and intra-abdominal without fascial infiltration, favoring parasitic leiomyoma over desmoid tumor. Scar Endometriosis with Peritoneal Implants: Endometriotic deposits may appear on ultrasound as irregular, heterogeneously hypoechoic nodules with internal echoes and peripheral vascularity. MRI classically demonstrates T1 hyperintense foci due to hemorrhage and T2 shading. Absence of hemorrhagic signal characteristics and lack of associated endometriotic lesions in our case argued against this diagnosis. Leiomyosarcoma: On ultrasound, leiomyosarcomas often present as heterogeneous solid masses with irregular or lobulated margins, areas of cystic degeneration or necrosis, and increased, disorganized vascularity. Rapid growth and infiltrative features support malignancy. No such imaging or histopathological features were observed in our case. Peritoneal Carcinomatosis: Ultrasound may reveal multiple hypoechoic peritoneal nodules, omental thickening, and ascites. PET-CT typically demonstrates increased metabolic activity, and tumor markers (eg, CA-125, CA 19-9) are often elevated. In our case, there was no ascites, PET-CT showed no abnormal uptake, and tumor markers were within normal limits. Lymphadenopathy: Pelvic or para-aortic lymph nodes usually appear as oval hypoechoic nodes with an echogenic hilum, following expected nodal chains. The lesion in our case lacked nodal morphology and was pedunculated from peritoneal surfaces, making lymphadenopathy unlikely. Abdominal Wall Desmoid Tumor: Desmoid tumors typically present on ultrasound as iso- to hypoechoic masses with poorly defined, infiltrative margins arising from musculoaponeurotic structures. Our lesion was well-circumscribed and intra-abdominal without fascial infiltration, favoring parasitic leiomyoma over desmoid tumor. Mild elevation in CA-125 and CA 19-9 may occur secondary to peritoneal irritation and does not imply malignancy. Persistent or progressive elevation, however, warrants exclusion of ovarian or gastrointestinal malignancy. Management of parasitic leiomyomas is guided by symptom severity and lesion burden. Asymptomatic or incidentally detected lesions can be managed conservatively with clinical and imaging surveillance [ 1 , 2 ]. Symptomatic or enlarging lesions require surgical excision, which remains the mainstay of treatment for diagnosis and symptom relief [ [1] , [2] , [3] , 5 , 6 ]. Surgical approach depends on lesion location and extent, with laparoscopic resection preferred for accessible lesions owing to lower morbidity and faster recovery [ 1 , 4 , 6 ]. However, complete excision is crucial to prevent recurrence, particularly in patients with prior morcellation or multiple implants [ 2 , 4 , 5 ]. Hormonal suppression therapy with gonadotropin-releasing hormone (GnRH) analogs or selective progesterone receptor modulators (eg, ulipristal acetate) may offer temporary reduction in lesion size, though recurrence is common after cessation [ 7 , 8 ]. Therefore, medical therapy is generally considered adjunctive or for patients unfit for surgery. Following excision, histopathologic evaluation is mandatory to confirm benign smooth-muscle origin and exclude leiomyosarcoma or peritoneal metastasis [ 3 , 9 , 10 ]. Complete surgical excision is curative in most cases, with rare recurrence if residual fragments persist. Awareness and intraoperative caution during morcellation are key preventive measures.

Parasitic leiomyoma represents an uncommon manifestation of uterine fibroids, characterized by ectopic implantation and autonomous growth of smooth-muscle tissue with an independent blood supply [ 1 ]. The pathogenesis is closely linked to prior uterine surgeries, particularly laparoscopic myomectomy using power morcellation, where small viable leiomyoma fragments may seed the peritoneum and develop under hormonal influence [ 2 ]. The reported incidence is increasing with the widespread use of minimally invasive procedures. Paul E. Steiner first described parasitic leiomyomas in 1939, and fewer than 200 cases have been reported to date, with an average latency of approximately 4 years postsurgery [ 3 , 4 ]. Parasitic leiomyomas may closely mimic malignant conditions such as peritoneal carcinomatosis both clinically and radiologically, posing diagnostic challenges [ 5 ]. The present report describes a rare case of multiple parasitic leiomyomas in the peritoneal cavity and abdominal wall following laparoscopic myomectomy with morcellation, highlighting the role of multimodality imaging, surgical, and histopathological correlation.