Cancer

Classifying a tumor by the type of cell from which it is derived is slightly more complex than classifying it by the type of tissue, since there are so many cell types. The main cell types include adenomatous cells (which are ductal or glandular cells), basal cells (found at the base of the skin), myeloid blood cells (granulocytes, monocytes, and platelets), lymphoid cells (lymphocytes or macrophages), and squamous cells (flat cells). Therefore it is possible for a cancer classified by its site of origin to be broken up into one of several cell types. For example, a skin cancer could be either a squamous cell carcinoma, a basal cell carcinoma, or a melanoma (from a pigment-producing cell).