Summary Early sarcomatous changes in neurofibroma are difficult to recognize either clinically or microscopically. The surgeon must view any neurofibroma that he is requested to remove, save for purely cosmetic or diagnostic reasons, with a high index of suspicion. Recurrence following surgical removal is very high and inadequate removal may accelerate the course of the disease. Metastasis and sarcomatous alterations in other neurofibromas are associated with recurrence. A case of neurofibrosarcoma of the breast associated with a recurrent neurofibrosarcoma of the back is presented, and the significance of the breast lesion in differential diagnosis is discussed.