What is the collection of pus surrounded by inflamed tissue called?

An abscess is defined as a localized collection of pus that is typically surrounded by inflamed tissue. This condition can arise due to infection, where the body's immune system responds to the presence of bacteria or foreign materials, leading to the accumulation of pus—a thick fluid composed of dead white blood cells, bacteria, and tissue debris.

The presence of inflammation around the abscess is a sign that the body is attempting to isolate the infection and prevent it from spreading. The inflamed tissue forms a barrier, which often results in redness, swelling, and pain in the affected area.

In contrast, a cyst is a sac-like structure filled with fluid or semi-solid material but is generally not filled with pus or associated with inflammation in the same way as an abscess. A fistula is an abnormal connection between two body cavities or a cavity and the skin, and does not pertain to pus formation or localized inflammation. A granuloma is a specific type of chronic inflammation characterized by a small area of inflammation that can encapsulate foreign materials or infectious agents, but it does not involve the collection of pus as seen in abscesses.

Therefore, the term that best describes the collection of pus surrounded by inflamed tissue is indeed an abscess.