Alveolar Soft Part Sarcoma

Definition

Sarcoma with large poorly cohesive cells with distinctive regular alveolar pattern

Large poorly cohesive round cells in nests
- Nodular growth pattern
- Composed of small nests or packets
  - At least focally, sometimes completely
- 25-50 cells per nest in cross-section on average
  - May vary from single cells to large numbers of cells
- Peripheral layer of cells frequently adheres to surrounding septum
- Rarely spindled or pseudoglandular pattern
Nests surrounded by thin walled vessels rather than connective tissue
- May produce sinusoidal pattern
Cytoplasm abundant, granular, eosinophilic
- Crystals reported in up to 80% of cases
  - Rod shaped
  - PAS positive, diastase resistant
  - May be irregular
- Glycogen usually present at least focally
  - PAS positive, diastase sensitive
- May have vacuoles
- May be clumped with clear areas
- May form globular inclusions
Nuclei large, regular, round and vesicular
- Nucleoli prominent
- Pleomorphism may be focal but not widespread
- Mitotic figures rare
- Multinucleated cells may be present
Vascular invasion frequent

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