RESUMEN
Myofibroblastic inflammatory tumors can occur in any human tissue. They are benign lesions and more common in young patients. We describe the case of a 41-year-old patient with a nodule measuring 2.5 x 1.5 cm in the superior lateral quadrant of the left breast. The pathological examination showed proliferation of the spindle cells in dense fascicles interspersed by colagen among frequent plasmocytes, lymphocytes and eosinophils, associated with scarce typical mitosis. In the same site ten years before the patient had undergone a nodulectomy and the diagnosis was a benign filloid tumor. The patient returned with a nodule in the surgical scar at follow-up and the incisional biopsy showed a malignant filloid tumor with a sarcomatous component. A mastectomy was performed.