Breast Cancer Cells May Spread Earlier Than Thought

According to the American Cancer Society one in eight American females will eventually develop breast cancer, which is the number two killer for women living in North America. Advanced screening methods have improved survival rates allowing for the tumors to be caught early. In such a stage the tumor is so small and confined that most doctors deem a simple lumpectomy to be sufficient to remove all the cancerous cells due to lack of metastasis. However, a sixteen percent recurrence rate within five years after the lumpectomy shows there is more to it than commonly thought. Now researchers at the Salk Institute for Biological Studies discovered that even these small tumors have the capability of seeding new tumors.

The early stage of breast cancer, where a tumor has not yet metastasized into the surrounding tissue, is called carcinoma in situ (CIS). This type of breast cancer is considered non-invasive. It is oftentimes located in a milk duct of the affected breast (ductal carcinoma in situ; DCIS). Until now scientists considered DCIS to be localized with only the ability to increase in size but no spread to other areas of the breast. Therefore, DCIS is considered to be a Stage 0 cancer, or "pre-cancerous" growth.

However, DCIS is still an uncontrolled growth of breast cells and requires removal of the tumor and surrounding tissue either by lumpectomy for a single growth or mastectomy for several DCISs in a breast. Radiation treatment may be recommended as well. This commonly depends on the size of the tumor and whether the pathological examination shows that the borders of the removed tissue are free of cancerous cells (clean cut). If the tumor is small and the pathological report indicates a clean cut, doctors often forego the radiation treatment. This common practice is based on the believe that the tumor had been caught in time and the removal was all that was needed to take care of this particular cancer development.