Analysis of phyllodes tumor recurrence according to the histologic grade

Local recurrence of phyllodes tumor (PT) of the breast is an adverse outcome that can result in sarcomatous degeneration. The aim of this study was to investigate the histologic and surgical factors associated with local recurrence. A total of 193 PT cases were studied: 145 (75.1 %) benign cases, 33 (17.1 %) borderline cases, and 15 (7.8 %) malignant cases. Stratifying our analysis according to histologic grade, we investigated the relationship between disease-free survival (DFS) and both histologic and surgical factors, including histologic grade, stromal cellularity, stromal atypia, stromal mitosis, stromal overgrowth, tumor margin, type of surgical procedure (local excision, wide excision, and mastectomy), surgical margin status, and radiation therapy. In the case of benign PT, all patients with local recurrences (3.4 %) had been treated with local excision, and all recurrent tumors were also benign. The local recurrence rate for locally excised benign PTs was not associated with surgical margin status or radiation therapy. In the case of borderline PT, local excision was associated with an increased local recurrence rate (P = 0.046). In malignant PT, small tumor size (≤4.0 cm) was associated with an increased local recurrence rate (P = 0.041). Univariate analyses indicated that surgical procedure (mastectomy < local excision < wide excision; P < 0.001) was significantly associated with shorter DFS in borderline PT. A positive surgical resection margin (P < 0.001) was associated with DFS in malignant PT. The factors associated with local recurrence differed with the histologic grade of PT, as did the features of local recurrence itself. In particular, benign PT had very low rate of local recurrence regardless of surgical margin status or radiation therapy, even when treated with local excision. In the case of benign PT, no recurrent tumors had worse histologic grades than the initial tumors.