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Cancer Genetics

Followup on Hereditary Breast Cancer

07/19/2001

Question:

I recently asked the question regarding hereditary breast cancer factors. Thank you for your response and information. After reading your information I have the following questions.

Let me pose this scenario. More than one woman in a family is diagnosed with the brac 1 or 2 genes. They have hereditary breast cancer, and more than one get breast cancer. Will they most likely have the same type of tumors and hormone receptors? Are there any studies or statistics of how many family members have the same type of tumors and receptors and how many don`t. Or am I completely off course and there is no relationship between family members and their breast cancer?

Answer:

You`ve asked a good question. Let me explain what the BRCA1 and 2 genes do which should help here. The BRCA genes (named for BReast CAncer)are involved normally in the repair of DNA. Whenever a cell divides in the body, DNA is copied -- all 2.5 million bits of genetic code in the cell. Mistakes can`t help but occur in that process. The cell has different mechanisms in place that correct the mistakes and the BRCA genes are just one aspect. The exact way in which they do this function has not been completely worked out.

If a person`s BRCA genes are not working normally (there is a mutation), these mistakes may not be corrected. If the mistake occurred in a section of DNA that is not critical, no problem follows. If the mistake is in an important section, such as a gene and particularly if the gene is involved in the regulation of the growth of the cell, that can cause abnormal growth and division of the cell. As mistakes accumulate in the cell, the cell becomes more and more `cancerous` in nature until it is capable of growing into a full-fledged cancer.

These mistakes accumulating in the cell are fairly random in their location within the DNA. If the mistake causes an excess amount of hormone receptors on the surface of the cell, the tumor may be receptor positive. If the mistake bypasses the hormone receptors, the tumor will be receptor negative.

Because the BRCA genes are at the beginning of this cancer-development process, a single family with a change in the BRCA genes can have any type of tumor or hormone receptor status occur in their family members. They are more likely to have receptor negative tumors simply because the multiple errors occurring in the DNA have more opportunity to generate a cancerous change via mechanisms other than excess receptor presence. They are also quite capable of having receptor positive tumors because of the same random location of DNA errors.

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Response by:

Judith A Westman, MD Judith A Westman, MD
Associate Professor, Clinical Internal Medicine, Pediatrics and Medical Biochemistry
College of Medicine
The Ohio State University