RESUMEN
Breast cancer within a fibroadenoma is rare and usually diagnosed postoperatively from pathological specimens. This paper reports a 54-year-old female with non-invasive carcinoma within a fibroadenoma, diagnosed preoperatively. She underwent a medical examination and mastopathy was suspected. On physical examination a mass 2 cm in diameter was palpated in the left breast. Ultrasonography showed a mass with smooth margins and uniform internal echoes, but cytology showed malignancy. Mammography showed a round mass with distinct margins and no calcification. As fibroadenoma, diagnosed by ultrasonography and mammography, and breast cancer, diagnosed by cytology, were not consistent results several core biopsies were performed. Needle biopsy showed proliferation of atypical epithelial cells; breast cancer within a fibroadenoma was diagnosed. MRI showed a circular mass with distinct, smooth margins and in a dynamic study, the mass showed irregular staining and the presence of early staining. Left lumpectomy and dissection of the left axillary lymph nodes was performed. Histological examination showed non-invasive lobular carcinoma occurring within a fibroadenoma.