What is defined as a closed sac with a membrane that develops abnormally in a body structure, typically filled with semisolid liquid?

A cyst is defined as a closed sac within a tissue that has a membrane and is often filled with a semisolid, liquid, or gaseous material. It can develop in various body structures as a result of abnormal growth or blockage. Cysts are typically benign and vary in size and location. Their formation can result from various causes, including infections, genetic conditions, or organ dysfunction.

In contrast, an abscess is a collection of pus that forms as a result of infection and inflammation, which is characterized by a different composition compared to the fluid typically found in a cyst. Tumors are abnormal growths that can be solid or fluid-filled but are generally associated with abnormal cell proliferation rather than clear fluid encased in a membrane. A granuloma is a specific type of inflammation, often a response to chronic infection or irritation, that results in the formation of a small area of tissue.

Understanding the characteristics of these different conditions helps clearly define a cyst as a specific type of structure formed in the body, distinguishing it from other types of lesions or growths.