Metastasis Definition and Process

Metastasis is the key characteristic of malignant tumors that describes the process where cancer cells invade surrounding tissues, enter the bloodstream or lymphatic system, and travel to distant parts of the body to form new secondary tumors.

This ability involves several steps:

• Detachment: Cancer cells break away from the primary tumor.
• Invasion: Cells invade nearby tissues and blood/lymphatic vessels.
• Circulation: Cells travel through the circulatory or lymphatic system.
• Arrest and Extravasation: Cells lodge in a new organ or tissue and exit the vessel.
• Formation of Secondary Tumor: Cells multiply to form a new tumor at the distant site.

Distinguishing Metastasis from Other Terms

It's important to differentiate metastasis from other related terms:

• Etiologic: Refers to the cause or origin of a disease, not the spread.
• Anaplasia: Refers to the loss of differentiation of cells and their normal appearance, a characteristic of malignancy but not the spread itself.
• Hyperplasia: Refers to an increase in the number of cells in an organ or tissue, often a benign response to a stimulus, unlike malignant spread.

Therefore, the specific ability of a malignant cell to detach and establish a new tumor elsewhere is termed metastasis.