CASE OF THE MONTH

April 2021

41 year old female presents for lumpectomy of a breast mass. Histologic sections show a fibroepithelial neoplasm with a pushing border, an increase in stromal cellularity, prominent “leaf-like” architecture, and increased mitotic activity (5-7 mitotic figures per 10 high power fields). Marked stromal atypia, stromal overgrowth, and heterologous elements are not seen. The diagnosis is BORERLINE PYLLODES TUMOR.

Borderline phyllodes tumor demonstrate features insufficient for a diagnosis of malignancy. Histologic findings include focally infiltrative border, increase in stromal cellularity, mild to moderate cytologic atypia, increased mitotic activity (5-9 mitotic figures per 10 high power fields), at most focal stromal overgrowth and an absence of malignant heterologous elements.
Borderline phyllodes tumors can have a 20% risk of recurrence and less than 10% may develop distant metastasis.






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