Vast Differences Found Between BRCA1 ER Positive and ER Negative Breast Cancers

We recently came across this data that we want to share with each of you:

BRCA1 germline mutations are one of the main causes of hereditary early-onset breast and ovarian cancer. Recent analysis of BRCA1 mutations conducted by researchers from the Institute of Cancer Research in London, provide additional insight regarding estrogen receptor status of the breast tumor. When a woman has a genetic confirmation of a positive BRCA1 mutation there is a difference between a diagnosis of an ER positive or an ER negative tumor. In more than 80% of cases, tumors arising in BRCA1 germline mutation carriers are estrogen receptor ER negative; however, up to 15% are ER positive.

Researchers reported a summary of the following characteristics found in the study:

Characteristic BRCA1/ER Negative BRCA1/ER Positive
Age  participants 54 52
Sex Female Female
Histological grade 3 2
Mitoses/10 HPF 81 15
ER Negative Positive
PR Negative Negative
HER2 Negative Negative
BRCA1 mutation c.124delA/p.Ile42TyrfsX8 c.4485-?_4986 + ?del/p.Ser1496CysfsX14
Somatic BRCA1 wild-type allele* Loss Loss
TP53 mutation c.927_928delTA c.951C > T
Molecular subtype Basal-like Luminal B
Tumor cell content GAP* (H&E) 71% (70%) 42% (60%)

This study confirms for Breast Health Navigators that a diagnosis of breast cancer, even when we have a confirmation that the tumor is BRCA1 positive, may vary in characteristics of the tumor.

The Journal of Pathology (2012); Pathological Society of Great Britain and Ireland

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