Near-diploid hyperploidy in early breast cancer (T1a,b) is associated with higher risk of lymph node involvement.

Due to the worldwide implementation of the mammographic screening program early breast cancer (T1a,b) has become more prevalent form of breast cancer. Although T1a,b breast cancers are generally associated with excellent prognosis, some of them, particularly those with lymph node involvement, has unfavourable outcome. Searching for additional prognostic factors, we investigated DNA content of 163 T1a,b cancers measured by DNA flow cytometry, and correlated it with regional lymph node status. T1a,b cancers were divided into four ploidy classes based on their DNA index (DI): hypodiploid (DI < 0.95), diploid (DI 0.95-1.05), low-hyperploid (DI 1.06-1.3), and high-hyperploid (DI > 1.3). Diploid T1a,b cancers were associated with negative lymph node status (p = 0.003). Among aneuploid cancers only low-hyperploid tumors were associated with positive lymph node status (p = 0.03). The histopathological features of low-hyperploid group of T1a,b cancers did not differ from the other three ploidy groups of cancers, except for lower S-phase fraction of tumor cells in low-hyperploid group compared to high-hyperploid group (p = 0.01). Our data showed that near-diploid hyperploid T1a,b cancers are associated with higher risk of lymph node involvement despite similar clinicopathological features shared with other ploidy classes of T1a,b tumors.