Which histologic findings are characteristic of phyllodes tumor (cystosarcoma phyllodes)?

Updated: Jul 23, 2019
  • Author: Donald R Lannin, MD; Chief Editor: John Geibel, MD, DSc, MSc, AGAF  more...
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All phyllodes tumors contain a stromal component that can vary significantly in histologic appearance from one lesion to another. [15]  In general, benign phyllodes tumors demonstrate a markedly increased number of regular fusiform fibroblasts in the stroma. Occasionally, highly anaplastic cells with myxoid changes are observed. A high degree of cellular atypia, with increased stromal cellularity and an increased mitotic count, is almost always observed in malignant phyllodes tumors.

Ultrastructurally, in both benign and malignant forms of phyllodes tumors, nucleoli may reveal a coarsely meshed nucleolonema and abundant cisternae in the endoplasmic reticulum.

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