Case of the month - January 2007 - discussion

Diagnosis - Myofibroblastoma

• A benign spindle cell tumour of the breast stroma composed of myofibroblasts



• Slow growing ranging in size from 1 - 10 cm



• First described by Toker in 1981 in men - subsequently identified in women also
  M:F ratio approximately 1:1



• Age range 40 - 90 years



• Similarities between this lesion and both the solitary fibrous tumour and the spindle cell lipoma
  

The following histological features are recognized:

• Expansile tumour with pushing borders



• Composed of short fascicles of spindle cells with intervening hyalinised collagen bands



• Necrosis absent and mitoses rare



• No entrapment of mammary ducts and lobules within the tumour



• Metaplastic fat or rarely, cartilage, may be found within the tumour

Differential diagnosis:

• Nodular fasciitis
• Inflammatory myofibroblastic tumour
• Fibromatosis
• Benign peripheral nerve sheath tumours
• Haemangiopericytoma
• Leiomyoma

Immunoprofile: