Sandi Shen, Shizhen Zhong, Gaofang Xiao, Haibo Zhou, Wenhua Huang

The aim of this study was to determine the relationship between parity and age at diagnosis, primary tumor size, axillary lymph node (ALN) metastasis, histological grade, and subtype classification in patients with breast cancer. Data from 392 patients with invasive breast cancer were collected and divided into four groups: nulliparous (parity 0), parity 1, parity 2, and parity ≥3. The relationship between parity and age at diagnosis was assessed using post hoc Dunnett's T3 test, and tumor size, the number of ALN metastases, and histological grade were analyzed using Spearman's rho test. Breast cancer subtypes were analyzed using the chi-square (χ(2)) test. The results showed that the mean age at diagnosis increased with increased parity, and the mean age of patients with parity ≥3 was significantly greater than that of patients with parity 0, parity 1, and parity 2. The mean age at diagnosis of patients with parity 2 was greater than that of patients with parity 1. There was no significant difference in the mean age between patients with parity 0 and parity 1 or parity 0 and parity 2. Parity was negatively correlated with ALN metastasis. Parity was not correlated with tumor size or histological grade and the proportion of the four subtypes in breast cancer. So, increased parity deferred the onset of breast cancer and inhibited the metastasis of ALN, but did not affect tumor size, histological grade, or the proportion of subtypes. Increased parity was a protective factor against breast cancer.