Periductal stromal sarcoma (PSS) is a type of rare malignant fibroepithelial tumor. PSS is a recently introduced diagnostic entity and there are few reports about radiological features of this tumor. Pre-operative diagnosis is difficult because it reveals similar symptoms with other benign and malignant tumors with absence of specific radiologic findings. We present a woman age 30 that underwent mammotome biopsy for a BI-RADS 4 lesion on her left breast and received histopathology diagnosis of a phyllodes tumor. Additionally, she underwent a wide excision depending on her histopathology diagnosis. Her final diagnosis was PSS. Six months later, no recurrence was detected. However, frequent follow-up is needed because PSS can develop into phyllodes tumor or entity of breast cancer.