Periductal Stromal Sarcoma of the Breast With Liposarcomatous Differentiation: A Case Report With 10-Year Follow-up and Literature Review.

A biphasic tumor with features of benign ductal elements and a malignant stromal component that lacks the architecture of a phylloides tumor represents a diagnostic challenge. A 35-year-old woman presented with a painful mass located in the upper inner quadrant of the right breast. A biopsy revealed histologically that the tumor had a multinodular architecture with malignant spindle cells forming cuffs around multiple open benign ducts. No leaf-like architecture was present. In addition, liposarcomatous differentiation was seen in focal areas. Immunohistochemical staining showed positive for CD34, vimentin and CDK4, and negative for ER, PR, Her2/neu, CD10, CD117, p63, bcl-2, cytokeratin, and MDM2. A diagnosis of periductal stromal sarcoma with liposarcomatous differentiation was established. Following excision with mastectomy and adjuvant chemotherapy, the patient was disease-free for 10 years. To our knowledge, this is the first case report of periductal stromal sarcoma showing liposarcomatous differentiation.