Sarcomas start when cells in connective tissues, called mesenchymal cells, begin to grow uncontrollably. These connective tissues include bone, cartilage, muscle, fat, and blood vessels. This uncontrolled growth forms a tumor, which can be either benign (non-cancerous) or malignant (cancerous). In the case of sarcomas, the tumors are malignant.
Here's a more detailed breakdown:
- Connective Tissues: Sarcomas arise from tissues that support, connect, and separate different types of tissues and organs in the body.
- Mesenchymal Cells: These are the precursor cells that differentiate into various types of connective tissue. Something goes wrong with these cells, causing them to divide and multiply rapidly.
- Uncontrolled Growth: Unlike normal cells, sarcomas don't respond to signals that tell them to stop growing or to die. This leads to a mass of abnormal cells forming a tumor.
- Malignancy: Sarcomas are malignant, meaning they can invade nearby tissues and spread (metastasize) to other parts of the body through the bloodstream or lymphatic system.
While the exact cause of this uncontrolled growth is not always known, several factors can increase the risk of developing a sarcoma:
- Genetic Predisposition: Some inherited genetic syndromes, such as Li-Fraumeni syndrome, neurofibromatosis type 1, and retinoblastoma, increase the risk of developing sarcomas. These syndromes involve mutations in genes that regulate cell growth and division.
- Radiation Exposure: Prior radiation therapy for other cancers can increase the risk of developing sarcomas in the treated area years later.
- Chemical Exposure: Exposure to certain chemicals, such as vinyl chloride and dioxins, has been linked to an increased risk of some types of sarcomas.
- Lymphedema: Chronic lymphedema (swelling due to lymphatic system blockage), particularly after breast cancer treatment, can increase the risk of developing angiosarcoma.
- Viral Infections: Kaposi sarcoma is caused by human herpesvirus 8 (HHV-8).
It's important to note that many sarcomas occur without any identifiable risk factors. Research continues to explore the complex mechanisms that lead to the development of these rare cancers.
