Carcinoma

Carcinoma is cancer that forms in epithelial tissue. Epithelial tissue lines most of your organs, the internal passageways in your body (like your esophagus), and your skin. Most cancers affecting your skin, breasts, kidney, liver, lungs, pancreas, prostate gland, head, and neck are carcinomas. There are three major types of carcinoma, including adenocarcinoma, basal cell carcinoma, and squamous cell carcinoma. 

Multiple genetic mutations can accumulate in a progenitor cell, like a stem cell, that can differentiate to create a specialized cell, and certain combinations of mutations can lead to the development of a cancer stem cell, which produces cancer cells and causes cancer.

Squamous cell carcinoma rarely metastasizes (spreads to other areas of the body), and when spreading does occur, it typically happens slowly. Indeed, most squamous cell carcinoma cases are diagnosed before cancer has progressed beyond the upper layer of the skin.