Breast Cancer and Mesothelioma

Breast cancer and mesothelioma may not initially seem to have much in common. One is most common in women and is the second leading type of cancer in women, while the other is rare and most often seen in men. Researchers, however, have found significant similarities, from diagnostic markers to symptoms and even treatments that slow the growth of tumors. There may even be a connection between asbestos and breast cancer.

Breast Cancer, Causes, and Risk Factors

Breast cancer is a malignant cancer of breast tissues, and it can occur in men and women, although it is much more common in women. In fact, this kind of cancer is the second most common type of cancer in American women, after skin cancer. Symptoms of breast cancer that usually lead a woman to see her doctor include lumps, a feeling of thickened tissue in the breast, an inverted nipple, and changes to the skin of the breast.

The exact cause of breast cancer is not known and may be complex and individualized. Cells in the breast tissue begin to grow abnormally and divide more rapidly to form a tumor, but why this happens is not understood. There are, though, many well defined risk factors for breast cancer, and exposure to asbestos may be one of them.

Well-known risk factors for breast cancer include having certain genes that have been identified as contributing to breast cancer. Others are being female and older, having a family history of breast cancer, being obese, never having been pregnant, being exposed to radiation, undergoing hormone therapy for menopause, and drinking alcohol.

Evidence Asbestos Exposure Contributes to Breast Cancer

There is some evidence that asbestos could be a contributing cause of breast cancer in some women. The conclusion that asbestos does contribute to this kind of cancer is not definite, as studies have shown mixed results. There is enough evidence to make a compelling case that asbestos exposure poses a risk for more than just mesothelioma.

In an Australian study from 2009, over 3,000 women participated and all were from a town that was home to an asbestos manufacturing company until 1966. These women were compared to the general population and it was found that while ovarian and cervical cancer rates were higher in those that lived near the factory, breast cancer rates did not vary. In a similar study from the UK, the results were different, with a slightly increased incidence of breast cancer in women who lived near asbestos manufacturing. Another British study found that among a group of female participants, those with asbestos fibers in their lungs were more likely to have breast cancer.

How asbestos could contribute to breast cancer is not understood. It causes mesothelioma and lung cancer because the fibers are inhaled and get lodged in the lungs and pleura. One idea for how this relates to breast cancer is that asbestos fibers move through lymphatic fluid to chest and breast tissue. Another hypothesis is that fibers actually pierce lung and pleural tissue and migrate into the chest wall.

Mistaking Mesothelioma for Breast Cancer

Mesothelioma is notoriously difficult to diagnose, and one of the main issues is that it is so easy to misdiagnose it as a different type of cancer, one that is more common, like breast cancer. This is problematic because a diagnosis directs treatment. With an incorrect diagnosis, a patient will get treatment for a cancer she does not have and not for the cancer that may actually be killing her.

One example of mistaking mesothelioma for breast cancer has been reported in the literature as a woman with metastatic mesothelioma, misdiagnosed as breast cancer. It is rare for mesothelioma to metastasize to the breast tissue. However, it can happen, and when a woman has symptoms of breast cancer, there is a possibility that the cancer actually originated in the pleural tissue.

The case study highlights the fact that misidentifying mesothelioma as breast cancer may be more common than doctors realize. A woman may be diagnosed with breast cancer and go through treatments without ever being given a diagnosis of mesothelioma. The symptoms of pleural mesothelioma, including chest pains, may be mistaken for symptoms of the breast tumor or the treatments used.

Even when a biopsy is done for a woman with breast cancer, signs that the cancer cells are really mesothelioma may be missed. This is because there is a high degree of overlap between breast cancer cells and mesothelioma cells in terms of cell structure and organization, and immunohistochemical markers.

When Breast Cancer Treatment Causes Mesothelioma

There have been reported cases of patients developing mesothelioma after being treated for breast cancer. It is rare, but the radiation used to shrink tumors in the breast has been shown to cause mesothelioma. Radiation therapy uses a high-energy beam aimed at tumors to kill cancer cells. Radiation also kills healthy cells, but the beam can mostly be targeted specifically at a tumor.

Radiation can also mutate the DNA in healthy cells, causing them to become malignant. To treat a breast tumor, the radiation must penetrate the skin and other areas of the chest cavity, including the pleura. In rare cases, this exposure causes damage that leads to additional cancer, in a few cases, cancer of the pleura, or malignant mesothelioma.

Breast Cancer Treatment for Mesothelioma

The same researchers that found mesothelioma could be misdiagnosed as breast cancers extended their research to find out if a breast cancer treatment could help battle mesothelioma. The treatment is a drug called aromasin, which blocks the action of an enzyme called aromatase. This in turn causes a reduction in the hormone estrogen, which slows tumor growth. Aromasin has been used to treat breast cancer with some success and it is generally well tolerated by patients.

Researchers used aromasin in laboratory mice with mesothelioma and found that the drug did slow the growth of cancer cells, as it did for breast cancer patients. Combined with a chemotherapy drug, aromasin treatment significantly reduced the sizes of mesothelioma tumors in the lab animals. It may be that the similarities in cells of both types of cancers, explains why the drug worked for breast cancer and mesothelioma.

Both breast cancer and mesothelioma are terrible diagnoses to receive. Treatment is challenging and may cause more side effects than the cancer itself. Prognoses are difficult as well and may not give patients much hope. The interesting research findings that these types of cancer may have a lot of similarities means that there is a high potential to develop better diagnostic techniques and better treatments that may extend or even save the lives of patients struggling with these types of cancer.