Phyllodes Tumors of the Breast

Phyllodes Tumors of the Breast
Phyllodes tumors are also known as cystosarcoma phyllodes. To the naked eye and under the microscope, they appear similar to fibroadenomas. Phyllodes tumors are more common in women and may present at any age. They present most commonly in the fifth decade of life. These tumors can be categorized as benign, borderline or malignant; however, most of them (35-64%) are benign. They account for fewer than 1% of breast cancers.

The most common symptom of a phyllodes tumor is a rapidly growing mass in the breast. Sometimes, with larger tumors, there may be blue discoloration of the overlying skin due to dilated veins. Tumors range in size between 5 and 7 cm. There are usually no masses in the axillary region, as these tumors (when malignant, see photo above) spread through blood vessels rather than through lymphatics. Ultrasound usually shows a mass with a smooth, lobulated border. Coarse calcium deposits may be visible. On mammography, phyllodes tumors appear as large, round masses with well-defined edges. Biopsy is needed to make the diagnosis and to classify these lesions as benign, borderline or malignant. Making the diagnosis with biopsy can be difficult due to overlapping similarities with other breast tumors, and surgical excision for diagnosis may be required.

These lesions must be differentiated from fibroadenomas. The standard treatment of phyllodes tumors, regardless of whether benign or malignant, is surgical excision (lumpectomy). For benign phyllodes tumors, excision of the tumor without wide margins is an acceptable approach. Narrow margins remove less breast tissue, which allows for better cosmetic results. Borderline and malignant phyllodes tumors are treated with surgical excision as well; however, wider margins of 1 cm are recommended. Mastectomy may be considered for particularly large lesions, where lumpectomy would leave an unacceptable cosmetic defect. With regards to malignant tumors larger than 2 cm in size, radiation therapy may be considered. This treatment is controversial, and management must be discussed with the patient’s care team. Chemotherapy and endocrine therapy have no proven benefit. Approximately 20% of malignant phyllodes tumors metastasize, with the lung being the most commonly affected organ. Treatment of metastatic disease requires a multi-disciplinary approach. Recurrence rates for malignant phyllodes tumors have been estimated to be up to 60%. Recurrence is most likely within the first 2 years following surgery.

Aydoğan F., Taşçı Y., Sagara Y. (2019) Phyllodes Tumors of the Breast. In: Aydiner A., Igci A., Soran A. (eds) Breast Disease. Springer, Cham First Online.
Tan BY, Acs G, Apple SK. Phyllodes tumours of the breast; a consensus review. Histopathology. 2016 Jan; 68(1):5-21.