Phyllodes tumor

Phyllodes tumor, also known as cystosarcoma phyllodes, is a rare fibroepithelial tumor of the breast which has some resemblance to a fibroadenoma. It is typically a large, fast growing mass that forms from the periductal stroma of the breast.

Epidemiology

Phyllodes tumors account for less than 0.3-1% of all breast neoplasms. It is predominantly a tumor of adult women, with very few examples reported in adolescents. The occurrence is most common between the ages of 40 and 60, before the menopause (peak incidence ~45 years). This is about 15 years older than the typical age of patients with fibroadenoma.

Clinical presentation

Patients typically present with a painless, rapid growing breast mass for which imaging is requested. 

Pathology

Its original term cystosarcoma phyllodes was coined in view of its leaflike pattern of growth. A phyllodes tumor may be considered benign, borderline, or malignant depending on histologic features including stromal cellularity, infiltration at the tumor edge, and mitotic activity. At histologic analysis, the tumor can resemble a giant fibroadenoma with both epithelial and stromal components being seen.

Fine needle aspiration is inaccurate, and even core biopsy has moderate sensitivity due to tumor heterogeneity causing inadequate sampling.

Radiographic features

The tumors can be quite large at presentation.

Mammography

Typically seen as non-specific large rounded oval or lobulated, generally well circumscribed, lesions with smooth margins. A radiolucent halo may be present. Calcification (typically coarse and plaque like) may be seen in a very small proportion. 

Ultrasound

General sonographic features are non-specific and can mimic that of a fibroadenoma ⁷.

On ultrasound, an inhomogeneous, solid-appearing mass is the most common manifestation. A solid mass containing single or multiple, round or cleft like cystic spaces and demonstrating posterior acoustic enhancement strongly suggests the diagnosis of phyllodes tumor. Vascularization is usually present in the solid components.

In practice, most lesions are indistinguishable from fibroadenomas on both mammography and ultrasound. This is why interval enlargement of a "fibroadenoma" is seen as an indication for a needle biopsy. Large lesions (i.e. >4 cm) may qualify for excision out of hand because needle biopsy may not be representative of the pathology in the whole lesion.

MRI

As with mammography, they are typically seen as oval, round, or lobulated masses with circumscribed margins. Signal characteristics can vary with histological grade ¹¹ but in general, are:

• T1: usually of low signal ⁸
• T2: can be variable ranging from homogenous low ⁸ to high ^4-5 signal
• T1 C+ (Gd): the solid components enhance after contrast administration
• dynamic contrast: the kinetic curve pattern can be gradual slow or have rapid enhancement

An inhomogeneous signal may rarely result in the context of accompanying hemorrhage or cystic spaces ⁹. Some suggest the inhomogeneous signal as indicative of benignity ¹⁰.

Treatment and prognosis

It is a locally invasive tumor. Treatment is usually with surgical excision. Large tumors may even require a full mastectomy. Both benign and malignant phyllodes tumors have a tendency to recur if not widely excised. Malignant degeneration is seen in 5-25% ⁴ (malignant phyllodes tumor).

After wide local excision, there is relatively frequent local recurrence (up to 25%) and up to 10% can metastasize. The mode of metastases in such cases is by haematogenous route. 

History and etymology

The name is derived from the Greek word: "phullon" meaning "leaf". Phyllodes tumors were first described in 1838 by Johannes Muller as "cystosarcoma phyllodes".

Differential diagnosis

For ultrasound and MRI appearances consider ^6,8:

• fibroadenoma of the breast
  • calcification is more common
• primary sarcoma of the breast