Sarcoma is a cancer originating in connective tissues, such as fat, muscle, bone, cartilage, and blood vessels. Sarcomas are fundamentally different from carcinomas, which arise from epithelial cells lining organs or the skin. Sarcoma is statistically considered a rare disease among adult malignancies, making it less familiar to the general public compared to more common diagnoses.
The Overall Picture: Incidence and Rarity
Sarcoma accounts for a very small fraction of all adult cancer diagnoses, typically representing less than 1% of the total cases reported annually in the United States. This incidence contrasts sharply with common cancers like breast, prostate, and lung cancer, which are diagnosed in hundreds of thousands of people each year. Despite its low percentage, the impact of sarcoma remains significant due to the complexity of treatment and its occurrence in younger populations.
Approximately 17,560 people in the United States will be diagnosed with some form of sarcoma in a given year, including both soft tissue and bone sarcomas. The vast majority of these cases are soft tissue sarcomas, estimated at 13,590 new diagnoses. Bone sarcomas are significantly rarer, accounting for about 3,970 new cases annually.
The disease is relatively more frequent in younger age groups, where it makes up a larger proportion of cancer diagnoses. In children, sarcoma accounts for approximately 15% to 20% of all childhood cancers. The overall rarity in adults means that many medical professionals outside specialized cancer centers may encounter only a few cases throughout their careers.
Categorizing Sarcoma: Subtypes and Variation
The term “sarcoma” is an umbrella term encompassing over 70 distinct subtypes, each with unique biological behaviors. This heterogeneity means a single overall incidence number can be misleading. The disease is broadly categorized into soft tissue sarcomas and bone sarcomas, with soft tissue types being about four times more common.
Soft Tissue Sarcomas (STS) develop in the body’s non-skeletal connective tissues and make up about 80% of all sarcoma cases. Even within this group, the commonness varies dramatically. For example, liposarcoma, which develops from fat cells, and leiomyosarcoma, which originates in smooth muscle tissue, are among the most frequently diagnosed soft tissue sarcomas in adults.
Bone sarcomas, such as osteosarcoma and Ewing sarcoma, are considerably less common than STS, making up the remaining 20% of cases. Some subtypes like rhabdomyosarcoma are predominantly seen in children, while others, such as leiomyosarcoma and liposarcoma, are typically diagnosed in older adults.
Demographics and Associated Risk Factors
Sarcoma can affect individuals of any age, but the age distribution varies significantly between the major categories. Soft tissue sarcomas are most often diagnosed in people over the age of 50, with incidence rates increasing with age. Conversely, certain bone sarcomas, like Ewing sarcoma and osteosarcoma, and some soft tissue types, such as rhabdomyosarcoma, are more commonly diagnosed in adolescents and young adults.
While most cases occur without a clear cause, several factors are known to increase the risk of developing a sarcoma. One established risk factor is previous exposure to high-dose radiation therapy. The sarcoma can develop years later within the previously irradiated area, although this accounts for less than 5% of all sarcoma cases.
A small number of sarcomas are linked to inherited genetic conditions. Syndromes like Li-Fraumeni syndrome and neurofibromatosis type 1 (NF1) involve mutations that predispose individuals to a higher risk of developing soft tissue sarcomas. Exposure to certain chemicals, such as vinyl chloride and the radioactive contrast agent thorium dioxide, has also been associated with an elevated risk for specific, rare subtypes of sarcoma.