RESUMO
We present the case of a 30-year-old lady who underwent a core needle biopsy for a BIRADS 4 lesion of her left breast and was diagnosed as having a cellular fibroadenoma. The final diagnosis after excision returned to be a periductal stromal tumor (PST). An extremely rare entity, the PST is actually classified as a subtype of phyllodes tumor, with specific criteria that are only found upon histological examination of the specimen. Care should be taken when considering the diagnosis of fibroadenoma based only on clinical, radiological, and biopsy findings. Any nonclassical, clinical, or radiological findings should prompt a wide excision. Prognosis is generally good when clear margins are obtained and in the absence of malignant heterologous elements.
