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Initially, it may not seem like breast cancer and mesothelioma have much in common. One is the second leading cancer type in women, while the other is rare and most often seen in men. However, researchers are discovering significant similarities between these two diseases. There are similarities in diagnostic markers and symptoms as well as similarities in treatments to slow tumor growth. There may even be a connection between breast cancer and asbestos, a dangerous mineral linked to mesothelioma.
Breast Cancer, Causes, and Risk Factors
Breast cancer is a malignant cancer of breast tissues. It can occur in both men and women, although it is much more common in women. After skin cancer, breast cancer is the second most common cancer type in American women. Symptoms of breast cancer include lumps, feeling of thickened tissue in the breast, inverted nipple, and changes to the skin of the breast.
The exact cause of breast cancer is unknown and may be complex and individualized. Cells in the breast tissue grow abnormally, dividing more rapidly to form a tumor. Why this happens is not understood. There are, however, many well defined risk factors for breast cancer. Asbestos exposure is one of these factors.
Well-known risk factors for breast cancer include certain genes identified as contributing to breast cancer. Other risk factors are sex, age, and family health history. Life style risks include obesity, never having been pregnant, exposure to radiation, hormone therapy for menopause, and alcohol consumption.
Evidence Asbestos Exposure Contributes to Breast Cancer
There is some evidence that asbestos could be a contributing cause of breast cancer in some women. Studies researching a link between breast cancer and asbestos exposure have been inconclusive. However, there is significant evidence of a link to make a compelling case.
In 2009 Australian study, over 3,000 women participated from a town that was home to an asbestos manufacturing company until 1966. These women were compared to the general population. It was found that ovarian and cervical cancer rates were higher in those living near the factory. However, breast cancer rates did not vary. In a similar UK study, results were different. In this study, there was a slightly increased incidence of breast cancer in women who lived near asbestos manufacturing. Another British study found that women with asbestos fibers in their lungs were more likely to have breast cancer.
How asbestos contributes to breast cancer is not understood. Asbestos composure causes mesothelioma and lung cancer after fibers are inhaled and become lodged in human tissue. It is possible that asbestos fibers move through lymphatic fluid to chest and breast tissue, potentially contributing to the development of breast cancer. Another hypothesis is that fibers pierce lung and pleural tissue and migrate into the chest wall.
Mistaking Mesothelioma for Breast Cancer
Mesothelioma is notoriously difficult to diagnose. One main issue in diagnosis is its similarities to more common cancers like breast cancer. This is problematic because diagnosis directs treatment. With an incorrect diagnosis, a patient will receive treatment for a cancer she does not have rather than the cancer that may actually be killing her.
One example of mistaking mesothelioma for breast cancer was reported in medical literature is a woman with metastatic mesothelioma, misdiagnosed as breast cancer. It is rare for mesothelioma to metastasize to the breast tissue. However, it is possible. When a woman has symptoms of breast cancer there is a possibility that the cancer actually originated in pleural tissue.
This case study highlights that misidentifying mesothelioma as breast cancer may be more common than doctors realize. A woman may be diagnosed with breast cancer and undergo treatment without being given a diagnosis of mesothelioma. The symptoms of pleural mesothelioma, including chest pains, may be mistaken for symptoms of breast cancer or the side effects of treatment.
Even when a biopsy is done, signs that cancer cells are mesothelioma may be missed. This is due to a high degree of overlap between breast cancer cells and mesothelioma cells in terms of cell structure, 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 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. As a side effect, radiation also kills healthy human cells.
Radiation can also mutate DNA in healthy cells, causing them to become malignant. To treat a breast tumor, radiation must penetrate the skin and chest cavity, including the pleura. In rare cases, this exposure causes damage that leads to additional cancer, including cancer of the pleura or malignant mesothelioma.
Breast Cancer Treatment for Mesothelioma
Researchers that discovered mesothelioma could be misdiagnosed as breast cancers extended their research to see if breast cancer treatment could help battle mesothelioma. The specific treatment is a drug called aromasin. Aromasin blocks the action of an enzyme called aromatase. In turn, a reduction in the hormone estrogen is triggered, slowing tumor growth. Aromasin has been used to treat breast cancer with some success and is generally well tolerated.
Researchers used aromasin in laboratory mice with mesothelioma and found the drug slowed the growth of cancer cells. Combined with a chemotherapy drug, aromasin treatment significantly reduced the sizes of mesothelioma tumors in the lab animals. Similarities in cells of both types of cancers could be responsible, explaining 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 and may not offer much hope for patients. Research suggests these types of cancer may have similarities means there is potential to develop better diagnostic techniques and better treatments for patients struggling with these types of cancer.
Page Medically Reviewed and Edited by Anne Courtney, AOCNP, DNP
Anne Courtney has a Doctor of Nursing Practice degree and is an Advanced Oncology Certified Nurse Practitioner. She has years of oncology experience working with patients with malignant mesothelioma, as well as other types of cancer. Dr. Courtney currently works at University of Texas LIVESTRONG Cancer Institutes.