2005 Stanford University School of Medicine
Surgical Pathology Criteria
Alveolar Soft Part Sarcoma
Alveolar Soft Part Sarcoma
Definition

Sarcoma with large poorly cohesive cells with distinctive regular alveolar pattern
Diagnostic Criteria

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
rouse@stanford.edu
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates:: 7/19/07, 8/4/10
Supplemental studies
Immunohistology

Muscle markers
TFE3 100% positive
Desmin About 50% positive
Muscle specific actin Variable, occasional cases positive
Smooth muscle actin Variable, occasional cases positive
Myoglobin Variable, occasional cases positive
MyoD1 All recent reports negative

S100 variable, occasional cases positive

HMB45 negative

Keratin negative

Chromogranin 1/5 positive

TFE3 also stains Xp11 translocation renal cell carcinoma

Focal and less intense reactions seen in melanoma, clear cell sarcoma, PEComa and angiomyolipoma
Genetic analysis

Unbalanced translocation der(17)t(X;17)(p11.2;q25) present in all cases studied, produces TFE3-ASPL gene product.

Detectable with two color break-apart FISH

Identical fusion transcript resulting from a balanced translocation is found in translocation-associated renal carcinomas.
Differential Diagnosis

Alveolar rhabdomyosarcoma

Metastatic carcinoma

Metastatic melanoma

Granular cell tumor

Paraganglioma
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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