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Can a Breast Biopsy Cause Cancer to Spread?

By Dr. Robert Zieve, MD

Many women today are asking this question and are hesitant to have a biopsy when one is

needed because of this concern. Let's look a bit further at this.

The short answer to this question is that if you have a biopsy and are found to have breast cancer, it has likely already spread outside of the breast before the biopsy was even done.

Here is the research on this:

Most breast cancers are invasive, either invasive ductal or invasive lobular, on biopsy. When

invasive tumors are discovered they are often already systemic, meaning that they have already spread.

At the time of a biopsy that finds a cancer, an invasive cancer has 1 billion malignant

cells. In women who have a stage 1 or 2 breast cancer, studies found 30-50% positive tumor cells in blood or bone marrow. The conclusion of these studies is that "hematogenous (through the blood) tumor cell dissemination into bone marrow is an early event in breast cancer development."

What about DCIS?

This has also been found to be true in women who are diagnosed on biopsy with DCIS (ductal carcinoma in situ), which is not really a cancer. Tumor cells in bone marrow were detected in 4 of 19 cases of pure DCIS (21.1%) and in 4 of 7 cases of DCIS with micro-invasion (57.1%).

While DCIS is not considered cancer, it is being treated as such in modern oncology, and often more aggressively than is called for, in part because it can develop into a cancer through these microinvasions.

This latter risk for women with the diagnosis of DCIS emphasizes the need to pay attention to terrain, or tumor microenvironment, and strengthen this in order to help prevent a DCIS from becoming an invasive breast cancer, which is its natural progression.

Bottom line:

If you are concerned that a biopsy of a lump in your breast will permit spread of the cancer, these studies have shown that the cancer has already spread outside of the breast even before a biopsy is done. Therefore, if you have a concern about a lump that you found or an area of suspicion on a 3D mammogram, it is best to have the biopsy, so you know whether or not you have a breast cancer. This provides you with peace of mind, knowing more about what is going on in your breast, and strengthens you to be able to make decisions as to your care and to plan on what type of practitioner or doctor(s) with whom to collaborate.

~Robert Zieve, M.D.

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