What is the primary difference between in situ and invasive carcinoma?

The distinction between in situ and invasive carcinoma primarily revolves around the behavior of the cancer cells in relation to surrounding tissues. In situ carcinoma refers to cancer cells that are confined to their originating site and have not penetrated the surrounding tissues. This characteristic makes in situ carcinoma non-invasive, indicating that it has not spread beyond the layer in which it originated, which is often a crucial factor in determining treatment options and prognosis.

On the other hand, invasive carcinoma has the ability to invade adjacent tissues and potentially metastasize to distant sites, often leading to a more complex clinical scenario. Understanding this primary difference is essential in pathology as it impacts the diagnosis, treatment plans, and outcomes for patients.