Leiomyosarcoma Arising in Vessels

Definition

Malignant neoplasm exhibiting smooth muscle differentiation arising in the lumen or wall of a vessel

Most commonly involves inferior vena cava or pulmonary artery
- May involve lumenal surface or invade wall
  - Invasion into adjacent soft tissue may be seen in venous cases
Smooth muscle differentiation
- Elongate eosinophilic cytoplasm
- Desmin or caldesmon stain usually positive
Requires any one of the following
- Cytologic pleomorphism or atypia
- Tumor cell necrosis
- Mitotic rate >4 per 50 HPF
Any tumor lacking the above histologic criteria should be considered a smooth muscle tumor of uncertain malignant potential as experience with such tumors is limited

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates:: 12/1/07, 7/15/10