Here's why:

* Mitosis is the process of cell division that creates two identical daughter cells from a single parent cell. This is essential for growth, development, and repair.

* Uncontrolled mitosis means that cells are dividing without the normal regulatory mechanisms in place. This leads to:

* Rapid growth: The uncontrolled division produces an abnormal number of cells.

* Abnormal cells: The cells produced may not be functioning properly or may have mutations that make them harmful.

* Tumor formation: The accumulation of these abnormal cells can form a mass called a tumor.

* Invasion and metastasis: Cancerous cells can break away from the original tumor and spread to other parts of the body, leading to more tumors.

Therefore, uncontrolled mitosis is the hallmark of cancer, a serious disease characterized by abnormal cell growth and spread.