Alveolar Soft Part Sarcoma

Julie C. Fanburg-Smith, MD

Aaron Auerbach, MD

Key Facts

Terminology

Alveolar soft part sarcoma (ASPS)
- Malignant soft tissue tumor of uncertain phenotype that mainly affects young adults and children
- Clustering alveolar-like growth pattern, separated by fibrous septa

Clinical Issues

Intramuscular
Hemorrhage
Lymphatic invasion
Deceptively indolent course
Distant metastasis
- To lung bone and brain
- Present in 25%

Microscopic Pathology

Solid type: Most common in infants in tongue and eye
Alveolar type: More common than solid type, usually buttocks, thigh in older child
High vascularity
PAS(+), diastase-resistant granular to crystalline cytoplasmic material, varies from few to all cells
Vimentin(-), desmin focally positive, MYOD1(-) (always cytoplasmic)
S100, keratins, CD34 all negative
TFE3(+)

Diagnostic Checklist

PAS(+) diastase-resistant granular to crystalline material is present in all cases (< 5-100% of cells)

Hematoxylin & eosin shows a typical example of alveolar soft part sarcoma with an alveolar pattern, mostly seen in older patients. The cells are polygonal and appear to slough into the “alveolar space.”

Hematoxylin & eosin shows alveolar soft part sarcoma with a solid growth pattern separated with thick, fibrous septa. This pattern is common in the tongue and ophthalmic region of younger patients.

TERMINOLOGY

Abbreviations

Alveolar soft part sarcoma (ASPS)

Definitions

Malignant soft tissue tumor of uncertain phenotype that mainly affects young adults and children
Clustering alveolar-like growth pattern, separated by fibrous septa

CLINICAL ISSUES

Presentation

Painless mass
Intramuscular
Hemorrhage
Lymphatic invasion

Prognosis

Deceptively indolent course
Distant metastasis to lung, bone, and brain present in 25%
Late recurrence and metastasis common
˜ 60% of patients have distant metastases
5-year survival rate is 65%

MICROSCOPIC PATHOLOGY

Histologic Features

Solid type: Most common in infants in tongue and eye
- Solid pattern
  - Sheets of polygonal cells
  - Separated by fibrous septa
Alveolar type: More common than solid type, usually buttocks, thigh in older child
- Alveolar pattern
  - Polygonal cells separated into nests by fibrovascular septa
  - Cells slough into center of “alveolus”
Eosinophilic cytoplasm
Eccentric nuclei with prominent nucleoli
Cytologic atypia rare
Mitotic activity low
High vascularity
Vascular/lymphatic invasion almost always present
Metastases to lung, bone, and brain

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