Phyllodes tumor is a rare fibroepithelial breast tumor that typically manifests in individuals between 40–50 years of age as a painless, multinodular breast mass. Unlike fibroadenomas, phyllodes tumors tend to increase in size more rapidly over time. On breast ultrasound, phyllodes tumors appear as a hypoechoic solid mass containing cysts; on mammography, they appear as a hyperdense mass. Biopsy is required for diagnostic confirmation. Histological findings of stromal cellularity and leaf-like architecture distinguish phyllodes from fibroadenoma. Phyllodes tumors are categorized as benign, borderline, and malignant according to the following features: border infiltration, mitotic activity, stromal atypia, and hypercellularity. Malignant or borderline phyllodes tumors can metastasize hematogenously. Surgical excision is recommended for nonmetastatic disease. Metastatic phyllodes tumors carry a poor prognosis; management (e.g., palliative surgery, chemotherapy) should be tailored to the individual. Phyllodes tumors have a high rate of recurrence after surgical excision.
- Painless, multinodular lump in the breast, with an average size of 4–7 cm
- Variable growth rate: may grow slowly over many years, rapidly, or have a biphasic growth pattern
Compared to phyllodes tumors, fibroadenomas tend to be smaller in size, remain the same size or grow slowly, and usually occur in younger (20–30 years) women. 
Follow age-appropriate diagnostic workup for a tumor are described here.. The findings specific to phyllodes
- Breast ultrasound: hypoechoic solid mass that may contain cysts 
- Mammography: hyperdense mass 
Phyllodes tumors may be indistinguishable from fibroadenomas on imaging, but features such as larger size, the presence of cysts, or a hyperdense mass on mammography should raise concern for phyllodes tumor. 
- Indications: all patients with suspected phyllodes tumor 
- Modalities 
- Findings 
Stromal cellularity and leaf-like architecture are key histological findings that distinguish phyllodes tumors from fibroadenomas. 
While phyllodes tumors are typically benign, some are malignant and have the potential to metastasize. Phyllodes tumors should be considered malignant until proven otherwise. 
- Benign phyllodes tumor: surgical excision
- Borderline or malignant phyllodes tumor: Assess for metastases (e.g., CT chest).