Phyllodes tumors of the breast are rare tumors that start in the connective (stromal) tissue of the breast. They get their name from the leaf-like pattern in which they grow (phyllodes means leaf-like in Greek). They are most common in women in their 30s and 40s, although women of any age can be affected. These tumors, which are usually painless, tend to grow quickly, but rarely spread outside of the breast. Most phyllodes tumors are benign. About 1 in 10 are cancerous. The underlying cause of these tumors in unknown. Surgery is the main treatment. Because the tumors can reoccur if they are not removed with enough surrounding tissue, the tumor and at least 1 cm of tissue should be removed. Cancerous phyllodes tumors are often treated with mastectomy. Close follow-up with frequent breast examinations are recommended after surgery.

at least 1 cm of the surrounding tissue. Some doctors feel that an even wider margin of healthy tissue should be removed (wide excision). Malignant phyllodes tumors may be treated more aggressively, with removal of wider margins of tissue or removal of part or all of the breast (partial or total mastectomy). Because spread to the underarm lymph nodes is rare, it is usually not necessary to remove them.

Phyllodes tumors of the breast do not respond to hormone therapy. Radiation and chemotherapy are not typically used as there is little evidence that these methods are effective for phyllodes tumors.

Because phyllodes tumors can come back, close follow-up with frequent breast examinations and imaging are recommended following surgery. This may include self and clinical breast exams, mammograms, ultrasound of the breast, MRI of the breast, and/or CT scans of the chest and abdomen (especially in malignant or metastatic cases).

Phyllodes tumors that are benign have an excellent prognosis following surgery. However, local recurrence is possible. If the tumor recurs locally, further surgery, including local excision or partial or total mastectomy typically results in a good outcome. The SArcoma and PHYllode Restrospective (SAPHYR) Study reported a three year survival rate for benign and borderline phyllodes tumors of 100 percent. Other studies have reported similar findings. Malignant tumors have a higher chance of coming back. If the tumor metasticizes, common locations include the lung, mediastinum, and skeleton. The five year survival rate for malignant phyllodes tumors has been reported to be 60 to 80 percent.