Phyllodes tumor

Last revised by Mohammadtaghi Niknejad on 25 Aug 2022

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 13.

Phyllodes tumors account for less than 0.3-1% of all breast neoplasms 13. 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 menopause (peak incidence ~45 years). This is about 15 years older than the typical age of patients with fibroadenoma.

Patients typically present with a painless, rapid growing breast mass for which imaging is requested. Average sizes can vary from 3 to 5 cm at presentation 13.

Its original term cystosarcoma phyllodes was coined in view of its leaflike growth pattern 13. 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 ref.

The tumors can be quite large at presentation. Imaging alone is not adequate to differentiate phyllodes tumor from fibroadenoma 13. Phyllodes tumor are frequently classified as BI-RADS 4 tumor 14.

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 13

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 13.

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.

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.

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 hematogenous route. 

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

For ultrasound and MRI appearances consider 6,8:

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Cases and figures

  • Case 1: on mammography
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  • Case 1: on ultrasound
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  • Case 2
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  • Case 3
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  •  Case 4
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  • Case 5
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  • Case 6
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  • Case 7
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  • Case 8
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  • Case 9: malignant
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