Purpose: In the last years, the incidence of breast cancer has been increasing; characteristic patterns of gene expression have emerged, reflecting molecular differences between previously known as well as newly defined subtypes of breast cancer. This study aimed to classify the molecular subtypes of breast cancers based on the expression profile of immunohistochemical markers and to evaluate their association with clinicopathological features.
Material and methods: A total of 173 cases of breast carcinoma were examined retrospectively using immunostains for estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2). Because the triple-negative phenotype, when defined by IHC using only these three markers, is not the optimal method for defining basal-like breast cancer, we need to use an additional marker--CK 5/6.
Results: The luminal type was the most common subtype in breast cancer (71.6%), which was followed by the basal subtype (21.9%). HER2 subtype were 2.8% from the total of cases, being associated with the highest rate of high-graded cases. Basal type is presented largely in premenopausal women and displayed aggressive features, such as large tumor size and poorly differentiated cancers. Luminal A included the highest percentage of patients older than 60 years, the highest proportion of stage I-II tumors and well/moderately differentiated lesions. HER2-type was more frequent in premenopausal women and showed a high percentage of positive lymph nodes.
Conclusions: These molecular differences have been shown to correlate very well with clinical features and survival, or even better than traditional histopathological parameters. The discovery of certain molecular characteristics of breast cancers has helped us to understand better the pathophysiology of disease and to develop more direct therapeutic strategies.