What does the medical term in situ mean?

The medical term "in situ" means in the original or normal position or location. It is used to describe a condition or process that is confined to its place of origin and has not spread to other parts of the body.

In situ is often used in the context of cancer to describe a precancerous or non-invasive condition. For example, carcinoma in situ (CIS) refers to a type of non-invasive cancer that is confined to the layer of cells where it originated. CIS is considered a pre-invasive stage of cancer and is considered more treatable than invasive cancer that has spread to other tissues.

The term in situ can also be used to describe other medical conditions, such as infections, inflammations, or developmental abnormalities, that are limited to a specific location. For example, otitis media in situ refers to a middle ear infection that is confined to the middle ear and has not spread to other parts of the ear or the body.