Alveolar Soft Part Sarcoma

Alveolar Soft Part Sarcoma
Low-power view shows an alveolar soft part sarcoma with a neoplastic cellular proliferation arranged in an alveolar growth pattern almost mimicking alveolated lung tissue.
Periodic acid-Schiff shows the characteristic intracellular crystals image typical of alveolar soft part sarcoma. This feature is almost invariably present in all cases.
TERMINOLOGY
Definitions
  • Malignant neoplasm of soft tissues
ETIOLOGY/PATHOGENESIS
Etiology
  • Although it has been speculated in the past as possible neurogenic or myogenic origin, its etiology remains unknown
CLINICAL ISSUES
Epidemiology
  • Incidence
    • Extremely rare tumor in mediastinal compartment
  • Age
    • Appears to be more common in young adults in 3rd decade of life
  • Gender
    • No gender predilection
Site
  • More common in soft tissues of extremities &/or head and neck
  • Anterior or posterior mediastinum
Presentation
  • Chest pain
  • Dyspnea
  • Cough
  • Asymptomatic
Treatment
  • Chemotherapy
  • Radiation therapy
  • Surgical resection
Prognosis
  • Variable
  • Tumor can metastasize
  • Short- and long-term survivals have been reported
MACROSCOPIC FEATURES
General Features
  • Fleshy, soft, and hemorrhagic tumor mass
Size
  • Varies in size and can be > 10 cm in diameter
MICROSCOPIC PATHOLOGY
Histologic Features
  • Alveolated growth pattern
  • Large polygonal cells
  • Well-defined cell borders
  • Ample cytoplasm
  • Eccentrically placed nuclei
  • Mild to moderate nuclear atypia
  • Mitoses are rare
  • Intracytoplasmic crystals
DIFFERENTIAL DIAGNOSIS
Rhabdomyosarcoma
  • 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
  • Cytoplasmic features
Pathologic Interpretation Pearls
  • Alveolar growth pattern
  • Large cells with ample cytoplasm
  • Presence of intracytoplasmic crystals
  • 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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Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Alveolar Soft Part Sarcoma

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