Parasitic leiomyomas after hysterectomy

A 44-year-old woman with a history of a laparoscopic myomectomy, hysterectomy, and right ovarectomy performed 5 years ago, was referred for ultrasound and CT imaging as part of her investigation for intermittent abdominal pain and discomfort persisting for 7 days. Her medical history was otherwise unremarkable.

A large, well-delineated ovoid mass is observed in the lower abdomen, with slightly heterogeneous enhancement. No cystic or necrotic areas or calcifications are identified. The surrounding bowel is displaced laterally and posteriorly, with prominent vascularization originating from the surrounding omentum. A smaller, morphologically similar mass is situated laterally to the aforementioned mass, with a broad attachment to the peritoneum and a preserved omental fat plane between the mass and adjacent bowel loops. No other abdominal or pelvic masses were detected.

The patient underwent complete resection, and histopathological examination was compatible with leiomyomas.

Background

Parasitic leiomyomas are uncommon variants of uterine leiomyomas that exist independently from the uterus and receive vascular supply from neighbouring structures [1]. It is hypothesized that they originate from leiomyomas that have detached from the uterus. Once free within the peritoneal cavity, they implant in a location and establish new vessels from surrounding tissue to survive and proliferate [2]. The increased use of laparoscopic surgery has led to a rise in iatrogenic parasitic leiomyomas following morcellation during myomectomy or hysterectomy, as small fragments may remain in the peritoneal cavity and subsequently implant [3]. Other subtypes of leiomyomas outside the uterus include benign metastasizing pulmonary leiomyomatosis, intravenous leiomyomatosis, or diffuse peritoneal leiomyomatosis [4].

Clinical Perspective

These tumours typically manifest in women of reproductive age, with a history of uterine surgery observed in approximately half of the cases. When they occur following surgery, diagnosis is often delayed, with a mean delay of more than 5 years. Patients are often asymptomatic but may present with nonspecific symptoms such as pain or bloating. Rarely, torsion of a pedunculated leiomyoma can occur [4].

Imaging Perspective

Tumour characteristics resemble intrauterine leiomyomas, appearing as well-defined masses with smooth margins. They may be singular or multiple and range in size from a few millimetres to several centimetres. A history of surgery is not always a prerequisite, particularly in cases of diffuse peritoneal leiomyomatosis. Leiomyomas can implant anywhere 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 [2]. A biopsy may be indicated, as imaging characteristics can be nonspecific, and tumour marker elevation may coincide [5].

Outcome

Parasitic leiomyomas are benign in nature and do not require treatment unless patients experience symptoms or there is significant compression of surrounding organs. To reduce their size, gonadotropin-releasing hormone agonists may be used, but the definitive treatment is surgical.

Take-Home Message / Teaching Points

The presence of multiple well-defined abdominal masses with smooth margins, particularly peritoneally or omentally based, in a woman of reproductive age should prompt consideration of parasitic or peritoneal leiomyomas, especially in those with a history of prior myomectomy.

Written informed patient consent for publication has been obtained.