In situ: In the normal location. An in situ tumor is one that is confined to its site of origin and has not invaded neighboring tissue or gone elsewhere in the body. For example, squamous cell carcinoma in situ is an early stage of skin cancer. From Healthy Resources 10 Rheumatoid Arthritis Symptoms How IL Inhibitors Work to Treat PsoriasisModerate to Severe UC: Targeted Solutions Featured Centers What Are the Best PsA Treatments for You?Understanding Biologics 10 Things People With Depression Wish You Knew