Intravenous leiomyomatosis: A retrospective case series of imaging findings and diagnostic challenges.

Intravenous leiomyomatosis (IVL) is a rare entity with nonspecific presentations, often leading to diagnostic challenges. Complete surgical resection requires precise preoperative imaging to map tumor extent. This retrospective case series summarized the imaging characteristics of 19 IVL cases and 1 endometrial stromal sarcoma (ESS) initially misdiagnosed as IVL, and compared the diagnostic utility of CT, MRI, and ultrasound. Among the 19 IVL cases, 7 were stage I, 5 stage II, 3 stage III, and 4 stage IV. Nearly half (47.3%) were asymptomatic, and 11 cases (57.9%) experienced initial missed or misdiagnosis. Only 3 cases demonstrated the typical worm-like extension of uterine fibroids into the parauterine veins. Pelvic lesions were categorized as solid (9 cases), predominantly solid (7 cases), or predominantly cystic (2 cases), with the latter considered atypical. Sixteen patients underwent enhanced CT/MRI; 2 presented with multilocular cystic masses consistent with ultrasound findings, while the remaining 14 exhibited uterine or pelvic soft tissue masses with heterogeneous density and mild-to-moderate enhancement. Enhanced MRI uniquely delineates pathognomonic worm-like contours and parametrial venous filling defects. For intravascular lesions, CT venous-phase imaging most clearly defined tumor extent, with both uterine and ovarian vein involvement being most common (47.4%, 9/19). Fourteen cases (73.7%) showed solid-density intravascular lesions, while 4 (21.1%) exhibited an atypical "sieve-like" pattern. The one ESS case had imaging features resembling IVL but showed significantly elevated PET-CT metabolic activity and CA125 levels. Ultrasound combined with CT/MRI enables comprehensive IVL evaluation. We recommend analyzing both pelvic and intravascular components, with attention to atypical manifestations.