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

Updated: Jul 20, 2021
  • Author: Donald R Lannin, MD; Chief Editor: John Geibel, MD, MSc, DSc, 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, [23] 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.

A small (N = 12) single-institution retrospective study by Johnson et al reported disproportionate rates of aggressive histopathologic features among black women with phyllodes tumor as compared with nonblack women. [24]

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