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Sarcomatoid Carcinoma/Carcinosarcoma

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  • Malignant biphasic or monophasic neoplasm demonstrating epithelial and mesenchymal differentiation.
  • Rationale for considering SC and CS as single entity is due to similar clinicopathologic features and poor prognosis.
  • Rare, only ~100 cases reported.
  • Histology falls into 3 categories:
    • Carcinoma admixed with sarcomatoid spindle cells (most common) (image A), (image B),
      & (image C).
    • Carcinoma admixed with sarcomatous component containing heterologous (or tissue not native) elements (malignant bone - osteosarcoma, cartilage - chondrosarcoma, skeletal muscles - rhabdomyosarcoma) (image D). (Called CS in older literature)
    • Pure spindle cell tumor with immunohistochemical and/or electron microscopic evidence of epithelial differentiation (e.g. keratin+).

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    • For carcinoma component, acinar adenocarcinoma is the most common pattern.
    • Sarcomatoid component is frequently composed of hypercellular high-grade spindle cells (undifferentiated spindle cell sarcoma).
    • Heterologous elements (non-native structures) present in 24% of cases, most commonly osteosarcoma.
    • Carcinoma component typically PSA+ or PSAP+.
  • Aggressive clinical course characterized by local recurrences and metastasis; 5 year survival of 41%.