Unusual polypoid endometriosis mimicking multiple solid ovarian masses following ovarian drilling

Polypoid endometriosis is a rare entity, with few cases reported in the literature. It is an uncommon manifestation of endometriosis that demonstrates histopathological features similar to those of an endometrial polyp and can mimic malignancy on imaging1. It is reported to be more common in postmenopausal women, sometimes in association with exogenous hormone therapy, such as tamoxifen2. We present a case of polypoid endometriosis, confirmed on pathology, mimicking multiple solid ovarian masses following an ovarian drilling procedure in a premenopausal patient. A 27-year-old patient with polycystic ovarian syndrome and worsening pelvic pain underwent laparoscopy. She was found to have Stage-3 endometriosis as per the Revised American Society of Reproductive Medicine classification. The patient demonstrated a right ovarian endometrioma adherent to the right pelvic side wall and peritoneal endometriosis in the cul-de-sac. She underwent fulguration of endometriosis, drainage and excision of the right ovarian endometrioma and bilateral ovarian drilling. One year later, she underwent ultrasound evaluation for worsening pelvic pain. Ultrasound showed a right ovarian cyst with internal low-level echoes, typical of endometrioma (Figure 1a). Adjacent to the cyst were multiple (at least three) solid-appearing, echogenic and vascular masses (Figure 1b). Given concerns regarding malignancy, pelvic magnetic resonance imaging (MRI) was performed, which also showed multiple solid masses in the right ovary, which enhanced post contrast (Figure 2). The patient subsequently underwent laparoscopic right salpingo-oophorectomy. Her right ovary was found to be replaced by a fixed firm mass, which was tightly adherent to the right pelvic sidewall and uterosacral ligament, and which was removed. The frozen section revealed benign endometrioma, and no further surgery was indicated. Final surgical pathology examination revealed that 90% of the right ovarian tissue was solid and 10% was cystic, with a final diagnosis of polypoid endometriosis. It is unclear whether the ovarian drilling procedure contributed to the unusual appearance of multiple solid masses. Endometriosis affects approximately 7% of women of reproductive age and increases the risk of ovarian cancer, particularly endometrioid and clear-cell cancer subtypes3. Parker et al. reviewed 24 cases of polypoid endometriosis, including pathological analysis, and found that the ovary was the second most common site of involvement after the colon2. In their study, polypoid endometriosis coexisted with classic non-polypoid endometriosis in 18/24 (75%) cases. Multiple sites of involvement were seen in 29% (7/24) of cases. In some cases, polypoid endometriosis was difficult to differentiate both clinically and pathologically from a low-grade Müllerian neoplasm. Ultrasound features of polypoid endometriosis typically include a multilocular mass with cystic components containing low-level echoes or solid tissue. The solid components can appear as solid vascular nodules or papillary projections, mimicking malignancy and ultimately requiring surgical resection4. MRI can be helpful when lesions exhibit signal characteristics similar to those of the endometrium, demonstrating high signal on T2- and diffusion-weighted images without low signal on the apparent diffusion coefficient map. A T2-hypointense rim has been described and is thought to represent fibrous tissue5. Ultimately, polypoid endometriosis is difficult to diagnose preoperatively and distinguish from malignancy. The presence of classic endometriosis findings and suggestive MRI features may be helpful in providing the correct diagnosis. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.