Objective  To investigate the clinicopathological features, immunophenotype, and differential diagnosis of intravenous leiomyomatosis (IVL).

  Methods  Clinical manifestations, morphologic features, and immunohistochemical staining results from 34 patients with IVL were retrospectively analyzed.

  Results  Patients were aged 24 to 61 years (mean 44.8 years), with the clinical manifestations included edema of low extremity, abdominal distention, hypermenorrhea, and other pelvic discomfort. In patients whose inferior vena cava and heart were also involved, the symptoms also included chest tightness, palpitation, and dyspnea. The morphologic changes were observed in uterine (n=14), pelvic veins (n=6), and inferior vena cava (IVC) (n=14); in 9 patients, tumors extended into right heart chamber through IVC. Microscopically, the tumors were composed of spindle-shaped cells with rare mitotic figure. The tumors were positive for SMA, ER, PR, and Desmin and negative for CD10 and HMB45. CD34 was positive in 4 patients and negative in the remaining patients. Ki-67 index ranged 0.3% -2.7%.

  Conclusion  IVL is a rare disease among women of child-bearing age. It can be histologically begign but biologically malignant, with specific morphologic manifestations and immunohistochemical features.