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Phyllodes Tumors (PTs) - Fibroepithelial Tumors of the Breast

By Jonas Wilson, Ing. Med.

Phyllodes tumors (PTs) are rare fibroepithelial tumors of the breast that display a wide range of biological behaviors. They account for up to 1% of all breast tumors. They are called “phyllodes,” which means “leaf-like” in Greek, because of the “leaf-like” pattern they grow in. However, they were known by over 60 different names before receiving the official terminology of PTs (from the World Health Organization).

The diverse biological behaviors of PTs range from fairly benign to aggressive with distant metastases. Tumors with the latter characteristics may degenerate on a histological basis to sarcomatous lesions, which are devoid of epithelial tissue. PTs were previously known as cystosarcoma phyllodes, but this terminology fell out of favor, because PTs are not true sarcomas by either biological or cellular characteristics.   

Epidemiology

PTs occur predominantly in women who are between the fourth and sixth decades of life. A few cases are seen in adolescent girls, but these are rare. The peak incidence occurs around the age of 45, in the perimenopausal period.

Some data suggests that the tumor grade increases with the average age at the time of diagnosis. Certain studies report a higher incidence in Latin American whites, in contrast to Asians, blacks and other whites.

These tumors are extremely rare in men, but case reports do exist. They are typically associated with gynecomastia (that is, the enlargement of the breasts in a man, due to a hormonal imbalance).  

Pathophysiology

In contrast to breast carcinomas, PTs tend to originate outside the breast lobules and ducts, and within the connective tissue of the breast. This connective tissue, also known as the stroma, is the component of the breast that consists of fibrous and fat tissue, within which the breast ducts, lobules and vessels are found. PTs contain mostly stromal cells. However, ductal and lobular cells may also be found. The etiology of PTs is poorly understood, but most patients present clinically with a breast mass that is painless and rapidly growing.

The texture of PTs is smooth, sharply demarcated and freely moveable. These tumors tend to be up to 5 cm on average, but may grow to several times this size. Studies report that up to 90% of these tumors are benign, but around 10 to 15% of them are malignant.

While benign tumors do not metastasize to distant sites, they tend to grow very aggressively and may recur locally. Their malignant counterparts behave like sarcomas and metastasize via the blood. The lungs are the most common site of metastasis. Other areas of spread include the heart, skeleton and liver. Most patients with metastasis cannot be cured. The survival rate for such patients is very low when they are followed up for three years from the start of treatment.  

Diagnosis and treatment

Mammography, core needle biopsy, fine needle aspiration, ultrasound, magnetic resonance imaging and color Doppler are some modalities which may be used to diagnose these tumors. Tumors that are benign with well-defined margins may be surgically removed, along with a margin of surrounding healthy breast tissue.

Mastectomy may be necessary for PTs that are very large in relation to the breast size. Tumors that have already spread to other sites are treated with chemotherapy. Their tendency to recur means that patients who have been treated need to be followed up closely with frequent examination and imaging tests of the breasts.

Reviewed by Dr. Liji Thomas, MD.

References

Further Reading

Last Updated: Aug 23, 2016

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