Alveolar Soft Part Sarcoma
Key Facts
Clinical Issues
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Incidence
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Extremely rare tumor in mediastinal compartment
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Appears to be more common in young adults in 3rd decade of life
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More common in soft tissues of extremities &/or head and neck
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Symptoms
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Chest pain
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Dyspnea
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Cough
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Asymptomatic
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Top Differential Diagnoses
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Rhabdomyosarcoma
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Positive for muscle markers, including MYOD1, myoglobin, and desmin
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Melanoma
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Positive for S100, HMB-45, and mart-1
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Paraganglioma
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Positive for neuroendocrine markers, such as chromogranin-A and synaptophysin
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Thymic carcinoma
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Carcinomas usually will show positive staining for epithelial markers, such as keratins and EMA/MUC1
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Diagnostic Checklist
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Alveolar growth pattern
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Large cells with ample cytoplasm
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Presence of intracytoplasmic crystals, especially using PAS histochemical stains
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Mitotic figures are rare
TERMINOLOGY
Definitions
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Malignant neoplasm of soft tissues
ETIOLOGY/PATHOGENESIS
Etiology
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Although it has been speculated in the past as possible neurogenic or myogenic origin, its etiology remains unknown
CLINICAL ISSUES
Epidemiology
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Incidence
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Extremely rare tumor in mediastinal compartment
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-
Age
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Appears to be more common in young adults in 3rd decade of life
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Gender
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No gender predilection
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Site
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More common in soft tissues of extremities &/or head and neck
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Anterior or posterior mediastinum
Presentation
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Chest pain
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Dyspnea
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Cough
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Asymptomatic
Treatment
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Chemotherapy
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Radiation therapy
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Surgical resection
Prognosis
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Variable
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Tumor can metastasize
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Short- and long-term survivals have been reported
MACROSCOPIC FEATURES
General Features
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Fleshy, soft, and hemorrhagic tumor mass
Size
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Varies in size and can be > 10 cm in diameter
MICROSCOPIC PATHOLOGY
Histologic Features
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Alveolated growth pattern
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Large polygonal cells
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Well-defined cell borders
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Ample cytoplasm
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Eccentrically placed nuclei
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Mild to moderate nuclear atypia
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Mitoses are rare
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Intracytoplasmic crystals
DIFFERENTIAL DIAGNOSIS
Rhabdomyosarcoma
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Positive for muscle markers, including MYOD1, myoglobin, and desmin
Melanoma
-
Positive for S100, HMB-45, and mart-1
Paraganglioma
-
Positive for neuroendocrine markers, such as chromogranin-A and synaptophysin
Thymic Carcinoma
-
Carcinomas usually will show positive staining for epithelial markers, such as keratins and EMA/MUC1
DIAGNOSTIC CHECKLIST
Clinically Relevant Pathologic Features
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Cytoplasmic features
Pathologic Interpretation Pearls
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Alveolar growth pattern
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Large cells with ample cytoplasm
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Presence of intracytoplasmic crystals
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Mitotic figures are rare
SELECTED REFERENCES
1. Daigeler A et al: Alveolar soft part sarcoma: clinicopathological findings in a series of 11 cases. World J Surg Oncol. 6:71, 2008

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