Breast, Malignant phyllodes tumour

Phyllodes tumours are fibroepithelial tumours that arise from intralobular stroma of the breast. The lesions have a 'leaf like' configuration, hence the Greek name 'phyllodes.' They mostly occur in the sixth decade, but can occur at any age. Criteria to differentiate between benign, borderline, and malignant include the degree of stromal cellularity and atypia, mitotic count, stromal overgrowth, and the nature of their tumour borders. While benign and borderline phyllodes tumours recur locally and rarely metastasize, malignant phyllodes tumours can develop distant metastases in about 15% of the cases. Excision with wide (at least 1 cm) margins with no lymph node dissection is the treatment of choice for malignant phyllodes tumours, with adjuvant radiation therapy sometimes given to large (over 10 cm) lesions or lesions with incomplete excision.

Findings in this case suggestive of malignancy include: marked hypercellularity, marked nuclear atypia, high mitotic count (up to 21 mitotic figures per 10 HPF), stromal overgrowth, infiltrative borders and heterologous elements in the form of adipocytes.