Phyllodes Tumor (Cystosarcoma Phyllodes)

Updated: Jul 20, 2021
  • Author: Donald R Lannin, MD; Chief Editor: John Geibel, MD, MSc, DSc, AGAF  more...
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Phyllodes tumor—once more commonly referred to as cystosarcoma phyllodes (from Greek kystis ["sac, bladder"], sarkoma ["fleshy tumor"], and phyllon ["leaf"])—is a rare, predominantly benign tumor that occurs almost exclusively in the female breast. [1, 2] Grossly, the tumor displays characteristics of a large, malignant sarcoma, takes on a leaflike appearance when sectioned, and displays epithelial, cystlike spaces when viewed histologically.

Because most of these tumors are benign, the term cystosarcoma is potentially misleading. Accordingly, the term currently favored is phyllodes tumor.


Pathophysiology and Etiology

Phyllodes tumor is the most commonly occurring nonepithelial neoplasm of the breast, though it represents only about 1% of tumors in the breast. [3]  It has a smooth, sharply demarcated texture and typically is freely movable. It is a relatively large tumor, with an average size of 5 cm (though lesions larger than 30 cm have been reported). The etiology of phyllodes tumors is unknown.

Because of limited data, the relative percentages of benign and malignant phyllodes tumors are not well defined. Reports have suggested, however, that about 85-90% of phyllodes tumors are benign and that approximately 10-15% are malignant. [4]

Although benign phyllodes tumors do not metastasize, they have a tendency to grow aggressively and can recur locally. [3]  Like other sarcomas, malignant phyllodes tumors metastasize hematogenously. Unfortunately, the pathologic appearance of a phyllodes tumor does not always predict the neoplasm's clinical behavior; in some cases, therefore, there is a degree of uncertainty about the lesion's classification.

The characteristics of a malignant phyllodes tumor include the following [5] :

  • Recurrent malignant tumors seem to be more aggressive than the original tumor
  • The lungs are the most common metastatic site, followed by the skeleton, heart, and liver
  • Symptoms of metastatic involvement can arise from as early as a few months to as late as 12 years after initial therapy
  • Most patients with metastases die within 3 years of initial treatment [6]
  • No cures for systemic metastases exist
  • Roughly 30% of patients with malignant phyllodes tumors die of the disease

Although most phyllodes tumors are benign, it is nonetheless important not to underestimate the potential of these lesions for malignancy. Moreover, some juvenile fibroadenomas in teenagers can look like phyllodes tumors on histologic examination; however, they behave in a benign fashion similar to that of other fibroadenomas. The difficulty of distinguishing among fibroadenomas, benign phyllodes tumors, and malignant phyllodes tumors may be vexing for even the most experienced pathologist. [7]



Phyllodes tumors occur almost exclusively in females, though rare cases have been reported in males. The tumors can develop in people of any age; however, the median age is the fifth decade of life.



If a phyllodes tumor is benign, the long-term prognosis is excellent after adequate local excision. However, the possibility for local recurrence after excision always exists, particularly with lesions that display malignant histology. [8, 9, 10] If the tumor recurs locally after excision, further local excision or total mastectomy is typically curative. Metastatic disease is typically observed in the lung, mediastinum, and skeleton. [5]

A study from the British Columbia Cancer Agency analyzed local recurrence, overall survival, and disease-free survival (DFS) in 183 patients with newly diagnosed benign (n = 83), borderline (n = 50), or malignant (n = 49) phyllodes tumors who were followed for a median of 65 months (range, 0.5-197 months). [11]  Overall, 8.7% experienced local recurrence, 4.4% distant metastasis, and 3.8% cause-specific death. With respect to individual subgroups, 5-year outcomes for women with benign, borderline, and malignant phyllodes tumors were as follows:

  • Local recurrence - 6%, 9%, and 21%, resectively
  • Overall survival - 96%, 100%, and 82%, respectively
  • DFS - 94%, 91%, and 67%, respectively

The 5-year local recurrence rates were 8% for women with negative margins, 6% for those with close margins, and 37% for those with positive margins. [11] The corresponding rates for intermediate, pushing, and infiltrative borders were 6%, 6%, and 33%, respectively. Positive margins and infiltrative tumor borders were significantly associated with increased local recurrence.


Patient Education

As for all breast neoplasms, self-examination remains the most important initial detection mechanism for phyllodes tumors. Appropriate teaching of this procedure is vital for early detection of all breast neoplasms.

For patient education information, see the Women's Health Center and the Cancer Center, as well as Breast Cancer and Breast Self-Exam.