Muscle Neoplasia

Primary neoplasia

• Rare in domestic animals
• Rhabdomyoma
  • Benign
  • E.g. laryngeal in dogs
  • Grossly:
    • Lobulated with no capsule
  • Histologically:
    • Large granular cells
    • Positive staining for myoglobin and desmin (immunoperoxidase technique)
    • Z - band material can be seen by electron microscopy
• Rhabdomyosarcoma
  • Malignant
  • Mainly in dogs
  • Metastases via lymphatics or venous routes -> in lymph nodes, lungs, spleen, heart and eleswhere in skeletal muscle
  • Grossly:
    • Pink masses with no capsule
  • Histologically:
    • Very varied
    • Cells with or without visible cross striations
      • Most easily seen with iron haematoxylin
      • Muscle tissue only contains myoglobin detected by immunoperoxidase method

Metastatic neoplasia

• Can occur to skeletal muscle (e.g. carcinoma, haemangiosarcoma)
• Infiltrative lipomas of dogs
  • Mature adipocyte tumours
  • Usually deep in subcutis or muscle
  • Infiltate along fascial planes or into muscles
  • Grossly:
    • Soft muscles
    • Yellow fat separating fasciculi
  • Histologically:
    • Well-differentiated adipose cells