[Medullary carcinoma of the breast: a malignant lesion mimicking a benign one]. / Carcinoma medular de mama: una lesión maligna que simula benignidad.

Medullary carcinoma of the breast is an unfrequent type of tumor. We present a case of medullary carcinoma of the breast. The patient presented with a palpable breast mass, corresponding on mammography to an obscured mass, which showed a cystic appearance with thick wall on sonography. We review the radiological findings of this type of tumor which should be considered in the differential diagnosis of lesions with well-circumscribed margins.