Fibromatosis of the female breast is rare. We dealt with a recurrent case of fibromatosis four months after a wide excision of the tumor. It was difficult to differentiate the tumor from carcinoma and only a pathological examination could lead to the final diagnosis. Ultrasonographic findings are so characteristic that we would like to emphasize the usefulness of ultrasonography not only in distinguishing between recurrence and operative scar but also in defining the diagnosis as fibromatosis of the breast.