Broad Ligament Endometriosis Presenting as a Solid Mass: A Diagnostic “Curveball”

Introduction

Endometriosis is defined as the presence of endometrial glands and stroma outside the uterine cavity. Endometriosis is a relatively prevalent condition, affecting ∼10% of women of childbearing age and is associated with pelvic pain and infertility. ¹ The most common sites for endometriosis are the ovaries and pelvic peritoneum. ² Peritoneal endometriotic deposits are usually small nodules or plaques; however, these deposits might rarely present as large solid masses. Endometriosis associated with the broad ligament is particularly infrequent, with only a few cases having been reported in the literature.^3–6

This article presents a rare case of tumor-like endometriosis associated with the broad ligament. Solid endometriotic lesions can have atypical imaging and macroscopic appearances and can cause diagnostic confusion. This case serves as a reminder for multidisciplinary teams to consider this pathology in the correct clinical and radiologic context.

Case

A 32-year-old premenopausal female (gravida 0, para 0) presented to the gynecology clinic with lower abdominal pain and swelling that had persisted for 2 months. Her past medical history included a left laparoscopic ovarian cystectomy and that she had been taking a combined oral contraceptive pill for many years.

Initial transabdominal and transvaginal ultrasound (US) showed an indeterminate left-adnexal mass; therefore, this patient underwent pelvic magnetic resonance imaging (MRI) for characterization. The MRI showed that there was a 7.9 × 4.9 × 5.4–cm left-adnexal lesion arising from the broad ligament, which displaced the anteverted fibroid uterus posteriorly and to the right (Fig. 1). The lesion was of a predominantly high T2-weighted (T2W) signal and a low T1-weighted (T1W) signal, and contained several foci of a high signal on the T1W fat-suppressed sequences consistent with a hemorrhagic component. There was no evidence of restricted diffusion. The normal left ovary was seen separated from the lesion. The differential diagnoses offered, based on these benign MRI characteristics, were an atypical broad ligament fibroid or a neurofibroma.

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FIG. 1.

Magnetic resonance imaging study showing a 7.9 × 4.9 × 5.4–cm solid-appearing mass (outlined by arrowheads) that is predominantly of a high T2-weighted (T2W) signal (A) and a low T1-weighted (T1W) signal (B). High-resolution T2W images (C) show the pedunculated mass arising from the left broad ligament, the stalk of which is highlighted (arrow). The mass contains foci of punctate hemorrhagic content anteriorly on the T1W fat-saturated images (D; arrow).

Following initial clinical examination and imaging investigations, the patient was referred to the gynecologic oncology department, given the potential complexity of surgery and the requirement for a radical but fertility-preserving procedure. She underwent open resection of the left parametrial mass with conservation of the uterus and the fallopian tubes and ovaries bilaterally.

Intraoperatively, there was a pedunculated, complex left pelvic mass, measuring ∼10 × 15 cm and originating from the left parametrial and paracervical spaces. The mass was of solid morphology, was relatively soft in consistency, and contained small cystic mucinous enucleations. It was almost completely adherent to the left pelvic wall with a significant associated neovasculature.

In order to remove the mass while preserving the left fallopian tube, left ovary and uterus, the left ureter was dissected from the level of the left common iliac artery to where it crossed the left uterine artery through the posterior leaf of the left broad ligament. The mass had to be dissected from the left external iliac vessels and the anterior branch of the left internal iliac artery, and was then excised from its attachment to the left parametrial and paracervical uterine wall. There was ∼300 mL of hemorrhagic peritoneal fluid that was sent for cytology examination.

Results

The patient had an uncomplicated recovery and was discharged to go home 3 days postoperatively. Three months later, she had a follow-up pelvic US that showed no sonographic evidence of residual endometriosis.

Microscopic examination of the excised broad ligament mass revealed the presence of endometrial stroma, within which inactive endometrial glands were present (Fig. 2), some of which were cystically dilated. These appearances were consistent with nodular endometriosis. There was no evidence of atypical hyperplasia or malignancy.

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FIG. 2.

Hematoxylin and eosin (H&E) stained × 20 (A) and × 40 (B) views of the histologic specimen showing cystically dilated endometrial glands and surrounding stroma. H&E × 200 (C) high-power view of endometrial glands lined by bland epithelium with minimal proliferation and endometrial stroma. Immunoperoxidase CD10 × 100 (D) shows that the stroma expresses CD10 strongly. Histopathologic findings are in keeping with nodular endometriosis.

Cytology of the bloodstained peritoneal fluid showed lymphocytes, macrophages, mesothelial cells, and a few neutrophils on a background of hemorrhagic material with no evidence of malignant cells.

Discussion

The imaging appearances of endometriosis are wide-ranging, but are most characteristically recognized as cystic ovarian structures with low-level internal echoes on US and homogenous nonfatty high T1W and variable T2W (including T2 shading) signal lesions on MRI that reflect internal blood products. ⁷ Conversely, extraovarian endometriosis presenting as a solid tumor within the pelvis is not frequently encountered in clinical practice, and such lesions related to the broad ligament are even rarer,^3,8–11 with only 2 cases documented in the literature by Itoga et al. ³ and Bergqvist et al. ⁹

Siegelman and colleagues described the MRI appearances of a series of solid endometriotic nodules. ¹² Most nodules that were characterized were of low T1W signal with punctate foci of a high T1W signal consistent with hemorrhage, which proved to be a recurrent feature in the cases of atypical endometriotic lesions. The majority of lesions were of low T2W signal with only 1 lesion producing a high signal on the T2W images. On pathological correlation, the low T2W signal regions corresponded to predominantly fibrous tissue, whereas the high T2W signal was related to dense glandular tissue on histology.

The etiology of tumor-like endometriosis is unknown. Interestingly, several case reports have associated tamoxifen therapy—an estrogen receptor antagonist used in the treatment of breast cancer—with the development of solid endometriosis on MRI.^3,6,10 This was not the case in the current patient.

Conclusions

Extraovarian endometriosis presenting as a tumor is uncommon, and the broad ligament is a very rare anatomical site. The current case included both of these findings. This case illustrates the need for clinicians and radiologists to be aware of tumor-like endometriosis and consider them in the differential diagnoses.