Retroperitoneal cyst with iliac stent involvement as primary manifestation of cystic echinococcosis

Cystic hydatid disease, also known as cystic echinococcosis, is an endemic parasitosis distributed across South Asia, the Middle East, Africa, South America, New Zealand, Australia, Turkey and Southern Europe1. Humans (i.e. intermediate hosts) can become infected by ingesting water or food contaminated with embryonated Echinococcus eggs. Hepatic hydatid cyst is the most common (65–70%)2, but in about 8–10% of cases, the hydatid cyst tends to appear in unusual sites, such as the appendix, retroperitoneum, omentum and mesentery, making preoperative diagnosis even more challenging. A 61-year-old woman was referred to our gynecology emergency department (Fondazione IRCCS Policlinico A. Gemelli, Rome, Italy) reporting pelvic pain, weight loss and anemia. She had a history of left nephrectomy due to kidney cancer, and deep vein thrombosis treated with bilateral iliac arterial stenting. Upon transvaginal ultrasound examination, a multilocular solid mass measuring 186 × 174 × 125 mm was identified in the right adnexal region (Figure S1), exhibiting well-defined borders, with areas of ‘low-level’ cystic content and a hyperechogenic solid component measuring 79 × 51 × 32 mm, showing moderate vascularization on color Doppler (Videoclip S1). No residual right ovarian parenchyma was detected. The mass was adjacent to the right common iliac vessels (Figure 1, Videoclip S2). Neither ascites nor carcinomatosis were observed. The uterus and left ovary were normal (Figure S2). Cancer antigen (CA125) level was unknown. Using only subjective assessment, the diagnosis was inconclusive. Three possible hypotheses were formulated: metastatic tumor, primary invasive ovarian tumor or retroperitoneal cyst. Applying the Assessment of Different NEoplasias in the adneXa (ADNEX) model without CA125, the mass was classified as malignant, and the highest relative risk was for Stage-I ovarian cancer.