Desmoid tumour of the breast

Desmoid tumour of the breast is a rare fibroblastic tumour whose spectrum ranges from being locally inert to aggressive and destructive, and represents 0.2% of all breast tumours. A 22-year-old woman, 2 years post-cosmetic augmentation mammoplasty with silicone implants, presented with a 6-month history of an enlarging mass in her left breast. Ultrasound showed a well-defined, hypoechoic mass arising within the muscles of the anterior chest, deep beneath the implant and not involving the underlying rib. Fine needle aspiration (FNA) showed features in keeping with changes associated with silicone implants. A provisional diagnosis of scarring and fibroblastic proliferation was made. The lesion was excised and the implant, noted to be intact, was exchanged. Immunochemistry showed strong positivity for vimentin and variable positivity for SMA and desmin, and patchy positivity for beta catenin. A final diagnosis of aggressive fibromatosis was made. Although the association of desmoid tumour and breast implants has been described, this case is unique as the FNA was highly suggestive of a silicone granuloma and the diagnosis of desmoid tumour was made on definitive pathology. The aetiology of desmoid tumours is reviewed and current treatment modalities discussed.