Although diagnosed less often, breast cancer in African American women (AAW) displays different characteristics compared to breast cancer in Caucasian women (CW), including earlier onset, less favorable clinical outcome, and an aggressive tumor phenotype. These disparities may be attributed to differences in socioeconomic factors such as access to health care, lifestyle, including increased frequency of obesity in AAW, and tumor biology, especially the higher frequency of triple negative breast cancer (TNBC) in young AAW. Improved understanding of the etiology and molecular characteristics of TNBC in AAW is critical to determining whether and how TNBC contributes to survival disparities in AAW.

Extensive genomic and transcriptomic heterogeneity in human cancer often negatively impacts treatment efficacy and survival, thus posing a significant ongoing challenge for modern treatment regimens. State‐of‐the‐art DNA‐ and RNA‐sequencing methods now provide high‐resolution genomic and gene expression portraits of individual cells, facilitating the study of complex molecular heterogeneity in cancer. Important developments in single‐cell sequencing (SCS) technologies over the past 5 years provide numerous advantages over traditional sequencing methods for understanding the complexity of carcinogenesis, but significant hurdles must be overcome before SCS can be clinically useful. In this review, we: (1) highlight current methodologies and recent technological advances for isolating single cells, single‐cell whole‐genome and whole‐transcriptome amplification using minute amounts of nucleic acids, and SCS, (2) summarize research investigating molecular heterogeneity at the genomic and transcriptomic levels and how this heterogeneity affects clonal evolution and metastasis, and (3) discuss the promise for integrating SCS in the clinical care arena for improved patient care.

Since the first link between blood type and cancer was described in 1953, numerous studies have sought to determine whether the histoblood ABO group is associated with tumorigenesis. In 2009, the first significant association between a SNP located within the ABO glycosyltransferase gene and increased risk of pancreatic cancer was reported. Here, we describe the history and possible functions of the histoblood ABO group and then provide evidence for a role of blood group antigens in the most common cancer types worldwide using both blood type and SNP data. We also explore whether confusion regarding the role of blood type in cancer risk may be attributable to heterogeneity within tumor types. Lay ABO encodes the protein responsible for defining blood groups as A, B, AB or O. Despite over a century of investigation, it is not well known whether the blood group antigens have a function or if they contribute to human health. Over the last 60 years, associations between blood type and cancer risk have been reported, although the data have often been conflicting. To better understand the possible role of the ABO blood group in tumorigenesis, we review the data for the most common tumor types worldwide.