Pathobiology of HER 2 positive small invasive (T1a,b) breast cancer: "A wolf in sheep's clothing".

Small invasive breast cancers (cancers with maximum diameter <1cm, T1a,b) become more prevalent form of breast cancer as a result of the introduction of breast cancer mammographic screening programs. Although associated with an excellent prognosis, T1a,b breast cancers are heterogeneous group of tumors with prognostically unfavorable subset of cases, primarily those with axillary lymph node metastases. To determine if the HER2 overexpression is associated with the prognostically unfavorable traditional clinicopathological features in this group of breast cancers, clinicopathological features (age, tumor size, histological type, histological grade, nodal status, hormone receptor status, proliferation index, lymphovascular invasion, ploidy) of 38 HER2 positive T1a,b cancers were compared with those of the control group consisting of 315 HER2 negative T1a,b cancers. The comparison of clinicopathological features was made using χ2 and t-test. HER2 positive T1a,b breast cancers were significantly associated with higher tumor grades (p<0.001), negative hormone receptors (p=0.008), presence of lymphovascular invasion (p=0.025), high proliferation index (p<0.001), and abnormal DNA content (p=0.04). We also noticed the higher frequency of lymph node positive cases in the HER2 positive group of cancers (p=0.05). There were no differences in age, tumor size and histological type between investigated groups. Our group of HER2 positive T1a,b breast cancers was associated with many unfavorable traditional prognostic factors, demonstrating that this subtype of early breast cancer has an aggressive biological phenotype which may have potential benefit from adjuvant chemo and immunotherapy.

Flow cytometric DNA hypertetraploidy tends to be more frequent in male than in female breast cancers.

The aim of the study was to explore possible differences in DNA flow cytometric characteristics, particularly differences in distribution of DNA indices of aneuploid clones, between male and female breast cancers. We retrospectively analyzed 31 male breast cancers. Clinicopathological and DNA flow cytometric characteristics of male breast cancers (patient age, tumor size, histological type, histological grade, axillary lymph node status, hormone receptor expression, ploidy, and S-phase fraction) were compared with that of the control group of matched female breast cancers. Hormone receptors and HER-2/neu were investigated immunohistochemically with additional chromogenic in situ hybridization (CISH) analysis of HER-2/neu 2+ cases. Ploidy and S-phase fraction were determined by DNA flow cytometry. Comparison with clinicopathological features was made using χ (2) and t test. Aneuploidy was found in 78% of the cases, with the predomination of hypotetraploid clones (39%), followed by tetraploid (23%) and hypertetraploid clones (16%). We found higher frequency of hypertetraploidy in male breast cancers (16 and 6%, respectively) than in the control group of matched female breast cancers. Clinicopathological features of hypertetraploid male breast cancers did not differ from that of non-hypertetraploid cancers. Higher frequency of hypertetraploidy among male breast cancers might indicate different cytogenetical evolutionary pathway between male and female breast cancer.