Case 122

A 54-year-old female with a 3.5 cm oval mass at her left breast

1. On close examination of the entire section, there is 7 mitosis/10HPF, what's the favored diagnosis?

   A: cellular fibroadenoma

   B: phyllodes tumor, favor borderline

   C: low grade fibroepithelial lesion/tumor

   D: phyllodes tumor, malignant

   
   

Answer

The correct answer is B. Although with this cellularity, cellular fibroadenoma is a differential but the 7/10 mitosis is not compatible with such interpretation.

COMMENT: Sections show a fibroepithelial tumor with area of leaf-like growth, increased stromal cellularity, and moderate nuclear atypia. Up to 7 mitotic figures per 10 high power fields is identified. No stromal overgrowth or heterologous elements are identified. There is no evidence of epithelial atypia or of carcinoma in the sample. Overall, the findings are in keeping with a phyllodes tumor, favor at least borderline. Defer to resection for more accurate classification.

Case credit: UCSD Pathology

Author: Wangpan Jackson Shi, MD