(75) Leiomyoma of a uterine remnant: Expand the differential for complex para-ovarian mass in patients with Mullerian agenesis

Background: Müllerian agenesis, an uncommon condition with an incidence of approximately 1 in 5,000 women, results in the absence of a vagina and uterus due to failed or incomplete formation of the Müllerian duct system. A uterine remnant with or without functional endometrium may be present unilaterally or bilaterally. While leiomyomas are common in the general female population with a prevalence of approximately 75% of women by menopause, leiomyomas arising from uterine remnant tissue are rare and associated symptomatology varies in the limited reported literature.

Case: A 40yo G0 with history of Müllerian agenesis status-post McIndoe neovaginoplasty as an adolescent was found to have a solid para-ovarian mass on a CT of the abdomen obtained in the setting of abdominal pain. Subsequent MRI revealed symmetric bilateral uterine rudiments with homogenous enhancement but no evidence of functional endometrium. Associated with the right uterine rudiment and right ovary, there was a 3.0 x 3.7 cm T2 hypointense lesion. Despite resolution of pain, surgical management was pursued due to concern for ovarian etiology. Upon laparoscopy, the pelvis was notable for bilateral uterine rudiments. There was an approximately 5 cm well-circumscribed, solid lesion discrete from the adnexa and arising from the right uterine remnant consistent in appearance with a subserosal leiomyoma. Left Müllerian remnant was without lesions. Remainder of the pelvic anatomy appeared normal. The mass was resected from the right uterine remnant and removed in a contained fashion. Histopathology of the 20.0g 6.5 x 6.0 x 5.0 cm mass revealed homogenous whorled smooth muscle consistent with a leiomyoma.

Comments: Müllerian agenesis varies in presentation of associated uterine remnant tissue. Uterine remnant tissue contains smooth muscle with or without the presence of endometrial tissue. Given the presence of smooth muscle in uterine remnants and the high prevalence of uterine leiomyoma in the general population, uterine remnant leiomyoma should be considered in the differential diagnosis of pelvic masses in patients with Müllerian agenesis. This case adds to a small body of 6 previously reported cases of leiomyomas arising from uterine remnant tissue, further describing the natural history of uterine remnant tissue in patients with Mullerian agenesis. Increasing the number of cases available to review helps provide comprehensive care to our patients with Müllerian anomalies from diagnosis in childhood and adolescence through adulthood. Additionally, given the possible close proximity of uterine remnant tissue to the ovary, it is important to consider uterine remnant leiomyoma as a possible etiology of solid, unilateral pelvic mass in patients with Müllerian agenesis.