Pathology dictionary -
A mass is abnormal tissue that takes up space in the body as it grows. The mass is usually surrounded by normal tissue.
The abnormal tissue inside a mass can be non-cancerous or cancerous. For this reason, mass is a descriptive word and not a diagnosis. The condition causing the mass can be determined after tissue is sent to a pathologist for examination under a microscope.
Examples of non-cancerous conditions that can cause a mass;
Immune reaction (such as an allergic reaction).
Blood (such as in a large bruise).
Examples of cancers that can cause a mass: