Medullary breast carcinoma (MBC) is a rare epithelial malignancy of the breast accounting for about 1-7% of all breast carcinomas. It is characterized by well-defined borders, a syncytial/solid pattern of growth of high grade atypical cells showing no glandular differentiation and a massive diffuse lympho-plasmacytic peritumoral infiltrate. Despite the high-grade atypias characterizing this neoplasm, MBC has been reported to have a better prognosis when compared with the common infiltrating duct carcinoma. MBCs typically lack estrogen and progesterone receptor (ER and PgR) expression and have a low incidence of ERBB2 overexpression. Genetically, they are often associated with BRCA-1 oncogene mutations and TP53 alterations. While MBC generally occurs in middle-aged women, ranging from 45 to 52 years of age, we report the case of a 18-year-old female patient which was diagnosed by means of fine-needle cytology sample.