In terms of tumor characteristics, what does the term "autonomous growth" refer to?

Autonomous growth refers to the ability of tumor cells to proliferate without the need for external regulatory signals that normally control cell growth and division. This characteristic is a hallmark of cancerous cells. Unlike normal cells, which require signals from the surrounding environment, such as growth factors, to divide, cancer cells can bypass these regulatory mechanisms. This independence from external cues allows tumor cells to grow and multiply uncontrollably, which contributes to the aggressive nature of cancers and their potential to invade surrounding tissues and metastasize to other areas of the body.

In contrast, the other options describe different aspects of cellular behavior. Growth dependent on external factors highlights the normal regulatory mechanisms in healthy cells, while growth limited to a specific location pertains to benign tumors rather than malignant ones. Additionally, angiogenesis, or the formation of new blood vessels, is a critical aspect of tumor growth and is often stimulated in cancer so that the tumor can secure a sufficient supply of nutrients and oxygen to sustain its uncontrolled growth.