9020/0 Phyllodes tumor, benign


Cystosarcoma phyllodes, benign


ICD-O-3 topography code: C50

Phyllodes tumours constitute one of the two major categories of fibroepithelial tumours of the breast (the other being fibroadenomas). Fibroepithelial breast tumours are biphasic lesions composed of an epithelial and a mesenchymal (stromal) component. The latter is quantitatively predominant and determines the overall appearance of the lesion.

In benign PTs, the stroma is usually more cellular than in fibroadenomas. The spindle-cell stromal nuclei are monomorphic and mitoses are rare, usually < 5 per 10 high-power fields (HPF) 1
Click to access Pubmed
Tan PH, Jayabaskar T, Chuah KL, Lee HY, Tan Y, Hilmy M, Hung H, Selvarajan S, Bay BH (2005)
Phyllodes tumors of the breast: the role of pathologic parameters.
Am J Clin Pathol 123: 529-40

. Stromal cellularity may be higher in the zone immediately adjacent to the epithelium, sometimes referred to as peri-epithelial or subepithelial accentuation of stromal cellularity.

See Phyllodes tumour for images detailed discussion.