Phyllodes Tumor (Cystosarcoma Phyllodes)

Updated: Jul 13, 2023
  • Author: Donald R Lannin, MD; Chief Editor: John Geibel, MD, MSc, DSc, AGAF  more...
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Practice Essentials

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 (the left more often than the right). [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.

Phyllodes tumors generally manifest as larger masses and display rapid growth. (See Presentation.) Overlying skin may be shiny and translucent enough to reveal underlying veins. A very large tumor may erode through skin and present as an external fungating breast mass. More typically, physical findings resemble those of fibroadenoma.

Complete excision, with accurate histologic examination and continued follow-up care, is the best way of treating phyllodes tumors. (See Treatment.) In most cases, wide local excision is indicated, with a rim of normal tissue included. If a satisfactory cosmetic result cannot be achieved with segmental excision, total mastectomy (with or without reconstruction) is an alternative; more radical procedures generally are not warranted. There is no proven role for adjuvant chemotherapy or radiation therapy.


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 is unknown.

Because of limited data, the relative percentages of benign and malignant phyllodes tumors have not been 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 (N = 182) from the British Columbia Cancer Agency analyzed local recurrence, overall survival, and disease-free survival (DFS) in 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 mo). [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.

In a study (N = 795) using data from the Surveillance, Epidemiology, and End Results (SEER) database, Chen et al investigated long-term (median follow-up, 126 mo) survival after breast-conserving surgery (BCS) versus mastectomy in patients with with T1-2/N0 stage malignant phyllodes tumor of the breast. [12]  BCS was found to provide benefits over mastectomy with respect to both overall survival (89.2% vs 81%) and breast cancer–specific survival (95.8% vs 90.1%).


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.