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Atypical epithelioid stromal cells are set in a somewhat loose matrix. It is not too cellular in this area, but the cells are clearly pleomorphic.

Other areas of the same tumor show much greater cellularity. Heterogeneity is common within a single tumor.

Yet another region with spindled cellular stroma and frequent mitotic figures. The stroma tends to condense around the epithelium.

The stroma is here is more sclerotic, with isolated malignant cells in clusters.

Bizarre stromal cells are randomly and diffusely present here.

Can you find the four mitotic figures?

The tumor exhibits an infiltrating edge into the surrounding fat.

Periglandular accentuation for Ki67 staining (a proliferation index).

C-kit staining is demonstrated two different areas of same tumor. Tan (2004) and Tse (2005) suggested that phyllodes tumor of increasing malignancy demonstrate increased C-kit immunoreactivity.

Similarly, CD10 is also expressed with increasing frequency in malignant phyllodes tumor.

This is a different malignant phyllodes that contain heterologous elements.


Phyllodes tumor are biphasic neoplasms composed of neoplastic stroma and benign epithelium. It is subdivided into benign, borderline and malignant categories based on histologic criteria. In benign phyllodes, characteristic cleft-like spaces are lined by a bilayer of epithelium and underlying myoepithelium. The stromal cells are bland, uniform and spindled. The tumor is also well-circumscribed.

Features that define a malignant phyllodes tumor include infiltrative margins, stromal overgrowth, cellular atypia and increased mitotic activity. Occasionally, liposarcomatous, chondrosarcomatous and/or osteosarcomatous differentiation may be seen.

Tse (2004) examined c-kit (CD117) staining phyllodes tumor and found that increased c-kit staining was seen in phyllodes tumor of increasing malignancy. For example, there was c-kit staining in seen 17 of 101 benign tumors (17%), 12 of 15 benign tumors (24%) and 13 of 28 malignant tumors (46%). Tan (2005) corroborated this finding using tissue microarrays and found that c-kit staining may be useful in predicting malignancy and recurrent disease in phyllodes tumor.

Similarly, Tse (2005) also found that CD10 (CALLA) is a useful marker in mammary fibroepithelial tumors and was expressed with increasing frequency from benign to malignant tumors. Stromal CD10 expression was positive in 1 of 33 fibroadenomas, 6 of 102 benign phyllodes tumours, 16 of 51 borderline malignant phyllodes tumours, and 14 of 28 frankly malignant phyllodes tumours.


Excision with a wide margin of negative tissues.


These tumors have a significant chance of local recurrence and metastatic behavior as well. Positive surgical margins are the key predictor of local recurrence.


Biphasic : Phyllodes Tumor


Fletcher CDM, ed. Diagnostic Histopathology of Tumors. 3rd Ed. Philadelphia, PA: Elsevier; 2007: 909-911.

O'Malley FP, Pinder SE. Breast Pathology: Foundations in Diagnostic Pathology. Philadelphia, PA: Elvesier; 2006: 118-124.

Tan PH et al. p53 and c-kit (CD117) protein expression as prognostic indicators in breast phyllodes tumors: a tissue microarray study. Mod Pathol. 2005 Dec;18(12):1527-34.

Tse GM et al. Increased c-kit (CD117) expression in malignant mammary phyllodes tumors. Mod Pathol. 2004 Jul;17(7):827-31.

Tse GM, et al. Stromal CD10 expression in mammary fibroadenomas and phyllodes tumours. J Clin Pathol. 2005 Feb;58(2):185-9.

Last updated: 2011-08-22
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