Phyllodes tumor of the breast

Phyllodes tumor of the breast (also known as cystosarcoma phyllodes or phylloides tumor) is a rare fibroepithelial neoplasm of the breast that arises from the periductal stromal cells. These tumors account for less than 1% of all breast neoplasms and are classified by the World Health Organization into three categories: benign, borderline, and malignant, based on histological features including stromal cellularity, mitotic activity, stromal overgrowth, and tumor margins. Phyllodes tumors predominantly affect women, with a peak incidence in the fourth and fifth decades of life, though they can occur at any age after puberty. The most common clinical presentation is a rapidly growing, firm, well-circumscribed breast mass that may become quite large. Patients typically notice a painless lump that increases in size over weeks to months. Large tumors may cause skin stretching, visible veins, and occasionally skin ulceration. Unlike breast carcinomas, phyllodes tumors rarely spread to axillary lymph nodes, but malignant variants can metastasize hematogenously, most commonly to the lungs, bones, and liver. The primary treatment for phyllodes tumors is wide local excision with adequate surgical margins, as local recurrence is a significant concern, particularly with borderline and malignant subtypes. Mastectomy may be necessary for large tumors or when adequate margins cannot be achieved with breast-conserving surgery. The role of adjuvant radiation therapy remains debated but may be considered for borderline and malignant tumors to reduce local recurrence risk. Chemotherapy has limited efficacy and is generally reserved for metastatic disease. Most phyllodes tumors are sporadic, though rare associations with Li-Fraumeni syndrome (TP53 mutations) have been reported. Prognosis is generally favorable for benign and borderline tumors, while malignant phyllodes tumors carry a more guarded prognosis with potential for distant metastasis.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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