A carcinoma is a type of cancer that arises in the cells that form the inner or outer surfaces of the body. It is the most common type of cancer in humans. However, the term is often used to describe cancer's where the origin of the tissue is unknown. Some examples of carcinomas are adenocarcinoma, squamous cell carcinoma, anaplastic carcinoma, large cell carcinoma and small-cell carcinoma. Carcinomas are the most common forms of cancer of the lungs (98% of cases), breast, prostate gland, large intestine and pancreas.