Intravenous leiomyomatosis with marked edematous degeneration mimicking IVC thrombus: A case report.

Intravenous leiomyomatosis (IVL) is a rare variant of leiomyoma characterized by proliferation of smooth muscle cells within uterine veins, with potential extension into the inferior vena cava (IVC), right atrium, or even pulmonary arteries. In advanced stages, IVL can lead to life-threatening complications, underscoring the need for accurate diagnosis and timely intervention. We report the case of a 40-year-old woman in whom an isoechoic structure within the IVC was incidentally detected on transabdominal ultrasonography and initially suspected to represent an IVC thrombus. Contrast-enhanced computed tomography (CT) demonstrated an enlarged posterior uterine wall with heterogeneous internal enhancement. A filling defect with subtle contrast enhancement within the dilated vessels extended continuously from the uterus through the pelvic venous plexus and right ovarian vein into the IVC. Magnetic resonance imaging (MRI) revealed heterogeneous high-signal-intensity lesions in the uterine myometrium with extension into the pelvic venous plexuses, ovarian veins, and the IVC, findings suggestive of a neoplastic process rather than thrombosis. The patient underwent surgical excision of the intravenous mass in conjunction with hysterectomy and bilateral salpingo-oophorectomy. Histopathological examination confirmed IVL with prominent edematous and degenerative changes. This case highlights the diagnostic difficulty of IVL with marked degeneration, which can closely mimic venous thrombosis, and emphasizes that a continuous pelvic-to-IVC extension, an associated uterine mass, and subtle contrast enhancement should strongly prompt the inclusion of IVL in the differential diagnosis.