The Phyllodes Tumor of the Breast
A Phyllodes tumor, which derives from the Greek word ‘phullon‘ or leaf, is a rare breast tumor usually effecting pre-menopausal women in their 40’s. It is difficult to genralize about the behavior of Phyllodes breast tumors.
Phyllodes tumors can either be benign, suspicious of malignancy or overtly malignant. Indeed, the diagnosis will depend upon the specific histological findings in each case.
Breast Phyllodes tumors account for about 0.5% of all breast neoplasms. A combination of stromal and epithelial cellular elements form the Phyllodes tumor.
Phyllodes breast tumors represent about 2% to 3% of all fibroepithelial breast tumors.
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Medical specialists often refer to a Phyllodes tumor of the breast as a ‘sarcoma’, because it develops in the connective tissue of the breast (the ‘stroma’). So, a Phyllodes breast tumor does not develop in the epithelial tissues that line the breast ducts and lobules.
Other names for Phyllodes tumors (PT) that you may hear include:-
- Phylloides tumor
- Cystosarcoma phyllodes
- Cystosarcoma phylloides
- Giant fibroadenomas
They tend to be large, very fast-growing breast tumors that evolve in a ‘leaf-shaped‘ growth pattern. Important to note is that not all Phyllodes breast tumors are breast cancer. However, your doctors will treat these types of tumors more seriously than other benign tumors, because some can become malignant.
Most phyllodes breast tumors are either low grade or benign
However, the majority of breast Phyllodes tumors are low-grade/benign tumors. Still, estimates for malignant presentations range between 20% to 50% of all cases.
Phyllodes breast tumors tend to develop in pre-menopausal adult women. Sometimes specialists will confuse Phyllodes tumors of the breast with a benign breast fibroadenoma. But Fibroadenomas tend to develop in women in their 20’s, not their 40’s and 50’s.
Clinical diagnosis of phyllodes tumor of the breast
Phyllodes breast tumors quite often present as a firm, bumpy, and smooth-sided mass. Furthermore, the breast skin covering the tumor might be warm to the touch and reddish in color.
Often patients will report the discovery of a lump that grows really quickly, even within a few short weeks.
Microcalcifications are generally not present in breast Phyllodes Tumors
On a mammogram, a phyllodes breast tumor will tend to be a lobulated, round or oval mass with a well-defined border. Phyllodes tumors tend not to be associated with microcalcifications.
Ultrasound cannot distinguish between Phyllodes Tumor and Fibroadenoma
On breast ultrasound, a phyllodes tumour will usually appear as a well-defined ‘macro-lobulated’ mass with heterogeneous internal echoes. Some phyllodes breast tumors show posterior acoustic enhancement, but not all.
So, if sonography suggests a fluid filling clefts or ‘elongated spaces’ in the mass, this would also point to a diagnosis of Phyllodes tumor.
However, neither mammogram nor breast ultrasound will be able to distinguish convincingly between a Phyllodes breast tumor, or a breast fibroadenoma. So, a biopsy will be necessary.
Histological features typical of Phyllodes Breast Tumors
The ‘hallmark’ microscopic feature common to all Phyllodes breast tumors is stromal hypercellularity and overgrowth.
Hypercellular stroma and ‘cleft like’ or cystic spaces with an epithelial lining, characterize the Phyllodes tumors. Into these cystic spaces typically grow projections of breast stroma tissues in a characteristic ‘leaf-like’ pattern.
Not all Phyllodes breast tumors show the classic ‘leaf-like’ pattern, however. Some of these tumors are simply solid and only vaguely lobulated.
The glandular elements of Phyllodes tumors are typically widely spaced, dilated and irregular with prominent side branches. Epithelial elements are quite often hyperplastic, and atypical columnar cell breast hyperplasia is not an uncommon co-finding.
Expression of epithelial ER and PR hormones is also common in phyllodes breast tumors, occurring at rates of about 43% to 84% respectively.
Diagnositc features of a Phyllodes breast tumors suggestive of malignant behavior
Some of the histological features of a breast Phyllodes tumor that would be more suggestive of malignancy include:-
- Mitotic activity
- Stromal overgrowth
- Stromal cellularity
- Infiltration at the tumor’s edge.
Probably the two most important histological determiners for the ‘grade’ of Phyllodes breast tumors are:-
- The speed at which the cells are dividing (mitosis)
- The number of irregularly shaped cells.
In terms of cell mitosis and potential malignancy, counts of 10 mitoses per 10 high power fields suggest a malignant tumor.
Malignancy in Phyllodes breast tumors also tends to be associated with increased patient age and tumor size. There is also some indication that ‘microvessel density’ and also the presence of the p53 protein, are also suggestive of malignancy in Phyllodes tumors.
Infiltrating margins are also strong indicators for malignancy, as well as the presence of necrosis and hemorrhage.
There is also some indication that an increase in the expression of c-kit (c-kit is a proto-oncogene that encodes a tyrosine kinase receptor, CD115), might also be more suggestive of a malignant tumor.
Up to 46% of malignant breast Phyllodes tumors are positive for c-kit expression, with a significantly lower rate in benign Phyllodes tumors. Pathologists also identify Ki-67 antigen expression as a marker for a more malignant Phyllodes breast tumor course.
Excisional biopsies and Phyllodes tumor
Generally speaking, physicians have greater confidence in the results of an excisional biopsy over fine needle aspiration when it comes to the cytological evaluation of a Phyllodes breast tumors.
Treatment and Prognosis for Phyllodes breast tumors
Surgeons tend to treat Phyllodes breast tumors by wide local excision. Historically, radiation and chemotherapy are not effective treaments for Phyllodes breast tumors.
It is difficult to generalize the risk of local recurrence or distant metastasis for Phyllode’s tumors. However, the histological grade is an important factor when it comes to risk of recurrence.
Benign Phyllodes tumors that are very large might even require a mastectomy. However, in general breast surgeons will usually postpone a mastectomy if there is evidence of a recurring tumor.
The outlook for benign Phyllodes Tumors is extremely positive
The outlook for women with benign Phyllodes breast tumors is very good. Indeed, there is a very low chance of recurrence after treatment for women over 45.
In some cases of Phyllodes tumor, the breast stroma may undergo metaplasia with underlying cartilage, bone, fat, and skeletal muscle. Sadly, When these additional metaplastic elements are also cytologically malignant, the prognosis is much poorer.
Local recurrence of a breast phyllodes tumor is very low
Following breast cancer surgery, medics estimate the recurrence rate of a Phyllodes tumor at just under 13%. Although less optimistic estimates place the recurrence rate as high as 20%. (Note: The higher number is associated with margins which were not completely clear).
However, local recurrence per se is not necessarily an indicator of malignancy with Phyllodes breast tumors.
The main indicators of breast tumor recurrence include:-
- grade classification
- evidence of stromal atypica
- stromal hypercellularity
- infiltrative borders.
Other indicators for a less likely recurrence of breast Phyllodes tumors include the presence of pseudoangiomatous stromal hyperplasia (PASH) and negative surgical margins.
Malignant phyllodes tumors metastize less than 20% of the time
Specialists estimate that metastases to distant areas occurs in around 19% of malignant Phyllodes breast tumors. However, it should be noted, that even some benign Phyllodes tumors have been known to metastize.
The metastatic spread of Phyllodes breast tumors seems actually to be associated with ‘haematogenous’ elements (blood oxygenization), and tends to occur in the bone, pleura, and the lungs.
Interestingly, less than 1% of Phyllodes breast tumors metastize to the axillary lymph nodes. For this reason, routine axillary node dissection is generally not indicated in treating aggressive phyllodes tumors.
Let’s do a little Q&A quiz…
What causes a Phyllodes tumor?
The causes for Phyllodes tumors are unknown. However, some inherited genetic disorders are known to increase the risk of developing a Phyllodes tumor.
Are phyllodes tumors cancerous?
Although most Phyllodes tumors are benign (not cancerous), some are malignant (cancerous) and some are also borderline (in between cancerous and non-cancerous). This depends on histologic features including stromal cellularity, infiltration at the tumors edge and mitotic activity.
How fast do Phyllodes Tumors grow?
They tend to grow very quickly in just a few weeks, to the size of 2 to 3 cms, or sometimes larger.
How do you treat a Phyllodes Tumor?
The common treatment is a wide local excision. Other than surgery, there is no other possible cure. Chemotherapy and radiation therapy are not effective what-so-ever.
What are the symptoms?
The most common symptom is a breast lump that you and your doctor can feel while examining the breasts.
Is a Phyllodes tumor painful?
What happens if a Phyllodes Tumor is not checked out?
If left unchecked, the lump can create a visible bulge as it pushes against the skin. It can also cause an ulcer or an open wound to form on the breast skin.
How are Phyllodes Tumors diagnosed?
- A physical examination
- a mammogram
- an ultrasound
- biopsy (core needle, or excisional)
How to prevent a Phyllodes Tumor?
Local therapy is aimed at preventing the tumor from coming back in the breast. Local therapy will include wide excision or mastectomy.
- Belkacémi Y, Bousquet G, Marsiglia H. (et al). (2007) Phyllodes Tumor of the Breast. Int J Radiat Oncol Biol Phys (2007). 70 (2): 492. https://www.ncbi.nlm.nih.gov/pubmed/17931796
- Moffat CJC, Pinder SE, Dixon AR, Elston CW, Blarney RW, Ellis IO. (2004) Phyllodes tumors of the breast: a clinicopathological review of thirty-two cases. Histopathology. 1995; 27: 205-218.3. https://www.ncbi.nlm.nih.gov/pubmed/8522284