[Young mammary Paget's disease patients with underlying breast invasive ductal carcinoma: clinicopathological features and prognosis].

To investigate the clinicopathological factors and prognostic status of young Mammary Paget's disease (MPD) patients with invasive ductal carcinoma (IDC). In this study, we defined the age at diagnosis below 40 years old as young patients, and retrospectively analyzed data from 123 MPD-IDC patients who were admitted at the Cancer Hospital Chinese Academy of Medical Sciences from June 2002 to February 2019. Patients were divided into the young group (≤40 years old, 15 cases) and the old group (>40 years old, 108 cases) according to the age of onset, and the clinicopathological characteristics and prognosis of the two groups were compared. Cox regression model analysis was used to analyze the prognosis influencing factors. The proportions of patients in the young group with non-menopausal, axillary lymph node metastasis, and Ki-67 index ≥15% were 93.3% (14/15), 73.3% (11/15), and 86.7% (13/15), respectively, which were higher than those in the old group [45.4% (49/108), 39.8%(43/108), and 60.2% (65/108), respectively] , with statistically significant differences (<0.05). At an average follow-up of 63.2 months, patients in the young group had a significantly shorter disease-free survival (DFS) compared with that of the old group (=0.012), while the difference in overall survival (OS) between the two groups was not statistically significant (=0.161). Multifactorial Cox regression analysis showed that axillary lymph node status was an independent influencing factor on OS (=3.339, 95% 1.121-9.943) in patients with MPD-IDC, while age was not. Compared with the old group, young patients with MPD-IDC have a higher incidence of axillary lymph node metastasis, high Ki-67 expression, and a shorter DFS, but age is not an independent influencing factor on DFS or OS in patients with MPD-IDC.