Fibromatosis of the breast is a benign but locally aggressive neoplasm, which has been described under various names including extra-abdominal desmoid tumour and aggressive fibromatosis. It is a rare condition, accounting for approximately 0.2% of all solid tumours of the breast. Clinically and radiologically the lesion mimics breast cancer and the definitive diagnosis is provided by histology. A high risk of local recurrence is a characteristic of this disease. Radical excision of the tumour with clear histological margins decreases the likelihood of recurrence. The possible association between breast implants and mammary fibromatosis has been reported. In this study we report a case of giant fibromatosis of the breast observed in a young patient and its extensive recurrence, involving all quadrants of the breast, the pectoralis major muscle, the rectus abdominis muscle sheath and the costal layer. The main clinical and pathological characteristics of this rare disease are illustrated, emphasizing the difficulties encountered both in the diagnosis of the primary lesion and in the management of its giant recurrence, particularly as regards the possibility of obtaining a radical surgical excision and the option of performing breast reconstruction.