Alveolar soft part sarcoma is a rare tumor and accounts for less than 1% of all adult soft tissue sarcomas and 1- 2% of non-RMS in children.
This tumor has a characteristic translocation: t(X;17)(p11;q25)
Generally involves the muscles and soft tissues of the lower extremities (buttocks, thighs and legs).
Metastatic disease is often present at diagnosis - frequently with multiple small pulmonary metastases. Bone and brain metastases may also occur.
- Multinodular, well circumscribed tumors
- Microscopically tumors have an alveolar structure. Center of alveolar space being formed by detachment of necrotic cells with surrounding capillaries
- Cells are large with abundant cytoplasm. Mitosis are rare.
- Pathognomic feature: Secretory process with the formation of cytoplasmic membrane-bound crystals (PAS positive, diastase resistant) often seen with electron microscopy. These granules contain monocarboxylate transporter 1.
Indolent disease with 7 year survival of 80% - but difficult to cure because of the high incidence of metastases.