Molecular Classification of Breast Cancer: Limitations and Potential

Abstract

Reverse transcription polymerase chain reaction and DNA microarrays are increasingly used in the clinic and in clinical research as prognostic or predictive tests. Results from these tests led to novel risk stratification methods and to new molecular classification of breast cancer. Some of these tools already complement existing diagnostic tests and can aid medical decision making in some situations. Better understanding of the molecular classes of breast cancer, independent of their prognostic and predictive values, may also lead to new biological insights and eventually to better therapies that are directed toward particular molecular subsets. However, there is substantially less experience with these emerging technologies than with the more established methods, the accuracy of which is often overestimated. This review discusses some of the limitations and strengths of current gene expression-based molecular classification of breast cancer. To provide context for this discussion, we also briefly examine the performance of estrogen receptor immunohistochemistry, which represents an essential part of the routine diagnostic workup for all breast cancer patients.

Molecular Profiling of Breast Carcinoma in Almadinah, KSA: Immunophenotyping and Clinicopathological Correlation

“…In the present study, we have investigated the frequency of individual and combined molecular subtypes of BC in a cohort of 115 Saudi women, based on IHC of ER, PR and Her-2/neu as a well-established method for classification (Pusztai et al, 2006;Pusztai, 2008). The immunostaining results of ER, PR and Her-2/neu in this study are in agreement with similar recent studies (Andrade et al, 2014;Elesawy et al, 2014).…”

“…Thus the recent BC research has now diverted from histological classification towards molecular classification. Development of new classifications based on immunohistochemical, genetic and molecular findings are subsequently in evolution (Pusztai et al, 2006;Pusztai, 2008).…”

Short-term outcome of primary operated early breast cancer by hormone and HER-2 receptors

“…The breast cancer specific survival in these patients correlated with hormone receptor status of the tumors for both HER-2-negative and HER-2-positive tumors. This has been confirmed in various ethnic populations [25][26][27][28][29][30]. Therefore, they can be used to estimate the prevalence of the five intrinsic subtypes in epidemiological studies without loss of their prognostic significance [22,25,31].…”

Gene expression of estrogen receptor, progesterone receptor and microtubule-associated protein Tau in high-risk early breast cancer: a quest for molecular predictors of treatment benefit in the context of a Hellenic Cooperative Oncology Group trial

“…Still, the power of these complex predictive models is at best moderate: patients may be undertreated or overtreated. Ultimately, we are unable to reliably predict the true binary outcome of recurrence versus no recurrence at the level of the individual, as these clinicopathological guidelines do not capture the rich molecular heterogeneity of the malignancy and are by no means able to pinpoint the exact clinical behaviour of breast tumors [6].…”