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4.8 cm lobulated breast mass was excised.
Malignant phyllodes tumours are fibroepithelial neoplasms with malignant stromal growth. Criteria for malignancy included stromal overgrowth, stromal hypercellularity, stromal cell atypia, mitotic activity, and invasive tumour borders. In this case, a very prominent liposarcomatous stromal component is present as a malignant heterologous component. Both well differentiated and pleomorphic areas can be seen. Although the histologic features are very similar, this heterologous element is molecularly distinct from soft tissue well-differentiated liposarcoma and is typically not associated with MDM2 and CDK4 amplification. Pleomorphic liposarcoma arising within a malignant phyllodes has also been reported. The prognostic significance of a heterologous component is unclear.
See Related Content for references:
1) Lyle et al., Histopathology 2016;68:1040-5
2) Inyang A et al., Breast J 2016;22:282-6
3) Bacchi et al, Ann Diagn Pathol 2016:21:1-6.