Coexistence of Ductal Carcinoma Within Mammary Phyllodes Tumor: A Review of 557 Cases From a 20-year Region-wide Database in Hong Kong and Southern China

The presence of malignant ductal carcinoma within phyllodes tumor is being underestimated, underdiagnosed, and underreported. However, the presence of ductal carcinoma is clinically relevant as it may alter clinical judgment and management. Here, we report 6 cases of ductal carcinoma (5 ductal carcinoma in situ and 1 invasive ductal carcinoma) arising from phyllodes tumor from a large multi-center database in Hong Kong and China. Introduction: Phyllodes tumor (PT) is an uncommon fibroepithelial tumor of the breast showing predominately proliferation of the stromal component. The presence of ductal carcinoma in situ (DCIS) or invasive ductal carcinoma is rare, with only a few cases reported in the literature. Methods: A retrospective review of a prospectively maintained database was performed. Patients who were treated for PT in 5 hospitals in Hong Kong and Shenzhen, China over a period of 20 years (1997-2016) were evaluated. All pathology slides were reported by specialist pathologists. Patients with coexisting ductal carcinoma were identified. Results: A total of 557 patients were included in this cohort; 363 (65.2%) patients had benign PT, 130 (23.3%) had borderline PT, and 64 (11.5%) had malignant PT. There were 6 (1.1%) patients with coexisting ductal carcinoma in the PT; 5 were DCIS and 1 was invasive ductal carcinoma. The median age was 46.5 years (range, 25-54 years). Ductal carcinoma occurred more frequently in malignant PT than in benign or borderline PT (4.7% vs. 0.6%; P = .02). However, malignant PT was not associated with higher DCIS grade (P = .1). All patients underwent surgery with clear resection margins. After a median follow-up interval of 70 months (range, 2-101 months), all patients remained disease-and recurrence-free. Conclusion: We report 6 additional uncommon cases of ductal carcinoma complicating PT. The presence of ductal carcinoma was not adverse prognosticator as these are usually incidental and situated within the harboring PT. (C) 2017 Elsevier Inc. All rights reserved.