Mass-Forming Deep Infiltrating Retroperitoneal Endometriosis Mimicking Liposarcoma: A Rare Diagnosis

Background:Endometriosis is defined as the ectopic functional endometrial tissue outside the uterus. It mainly affects women of reproductive age. Although its exact cause is unknown, it is an estrogen-dependent condition, which can be asymptomatic, or present with varying degrees of pelvic pain. It is most commonly seen in the pelvis, involving peritoneum, ovary, rectovaginal septum, and ureter. A rare form of deep infiltrating endometriosis (DIE) also occurs, involving uterosacral ligaments, rectovaginal space, upper third of the posterior vaginal wall, bowel, and urinary tract. Case:In this study, we report a case of a 30-year-old woman, who presented with pain in abdomen for 5 months, associated with menstrual cycle and was clinically and radiologically diagnosed as retroperitoneal liposarcoma. Results:On histopathologic examination, many well-formed endometrial glands with adjacent stroma, lying within fibrous interstitial tissue, were seen and the fatty areas showed mature adipose tissue and hemosiderin-laden macrophages, merging with the areas of endometriosis. Conclusions:DIE should be kept in mind in young females with a retroperitoneal soft tissue mass, presenting with pain associated with menstrual cycle.