Phyllodes tumors of the breast: Real world data from a multi-institution cohort

Phyllodes tumors (PT) are rare breast lesions arising from fibroepithelial stroma and may be hard to clinically distinguish from fibroadenomas. They are defined as benign, borderline or malignant. The purpose of this study was to describe diagnostic workup and surgical management, and to investigate incidence of local recurrence (LR) and overall survival (OS) in relation to tumor subtype, size, age, surgical margins, surgical method, and year of diagnosis.

Retrospective cohort study of all patients surgically treated for a PT in Stockholm, Sweden from 1999 to 2018. Descriptive analyses were performed, and regression models were used to analyze associations between selected covariates and LR and OS.

Among 191 patients, 132 were treated for a benign PT, 40 for a borderline PT and 19 for a malignant PT. Preoperatively, results from diagnostic workup were often ambiguous, and only 45.6 % of cases had a preoperative diagnosis of PT. Initial surgery was breast-conserving in 93.2 % of patients. Recurrences occurred in 10.5 % of the total cohort. 5-year and 10-year OS was 96.1 % and 93.5 %, respectively, for the entire cohort. In a multivariable analysis, neither covariate was associated with risk of LR. Distant recurrences were only detected among patients with malignant PT.

In the workup of PT, common diagnostic methods such as FNAC, CNB, and mammography may be unreliable, and clinical suspicion plays a critical role in guiding pre-operative decision-making. We found no association between surgical margins and rate of LR or OS. We found no evidence of metastatic potential in benign or borderline PT.