Surgical Pathology Criteria

Alveolar Soft Part Sarcoma

Differential Diagnosis

Alveolar rhabdomyosarcoma Alveolar Soft Part Sarcoma
Variably shaped alveolar spaces Regular alveolar spaces
Fibrous septa around nests Thin walled vascular septa
Cells generally 10-30 microns diameter Cells larger
Pleomorphic nuclei Only mild pleomorphism
Dense nuclei Vesicular nuclei
Small nucleoli Prominent nucleoli
No crystals Crystals in up to 80% of cases
Uniformly desmin, actin positive Occasionally desmin, actin positive
Frequently MyoD1 positive MyoD1 rare or negative
Translocations t(2;13) or t(1;13) der(17)t(X;17)(p11.2;q25)

 

Granular cytoplasm and / or nesting pattern of cells in the following may raise the question of alveolar soft part sarcoma

Metastatic Carcinoma Alveolar Soft Part Sarcoma
Keratin positive Keratin negative
Desmin, actin negative Occasionally desmin, actin positive
May have pleomorphic nuclei Only mild pleomorphism
Unusual in young adults Usually young adults
Morphologically similar carcinomas include renal cell and ovarian clear cell

 

Metastatic melanoma Alveolar Soft Part Sarcoma
Uniformly S100 positive S100 variable
HMB45 85% positive HMB45 negative
Desmin, actin negative Occasionally desmin, actin positive
Pleomorphic nuclei Only mild pleomorphism
Unusual in young adults Usually young adults

 

Granular Cell Tumor Alveolar Soft Part Sarcoma
Uniformly S100 positive S100 variable
No regular nests of cells Regular nests of cells
Dense granular cytoplasm Variable granularity, frequent vacuoles

 

Paraganglioma Alveolar Soft Part Sarcoma
Usually small nests (zellballen) Usually large nests
Surrounded by fibrous tissue Surrounded by thin walled vessels
Small to medium size cells Large cells
Dense nuclei, often spiculated chromatin Vesicular nuclei
Inconspicuous nucleoli Prominent nucleoli
Chromogranin positive One case reported chromogranin positive
S100 sustentacular cells frequent No sustentacular cells
Desmin, actin negative Occasionally desmin, actin positive
Does not occur on extremities Frequently involves extremities

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