Carcinoma is a category of types of cancer that develop from epithelial cells. Specifically, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that arises from cells originating in the endodermal, mesodermal or ectodermal germ layer during embryogenesis. Carcinomas occur when the DNA of a cell is damaged or altered and the cell begins to grow uncontrollably and become malignant. The cell type from which they start; specifically: Epithelial cells - carcinoma, Non-hematopoietic mesenchymal cells - sarcoma, Hematopoietic cells, Bone marrow-derived cells that normally mature in the bloodstream- leukemia, Bone marrow-derived cells that normally mature in the lymphatic system - lymphoma, Germ cells- germinoma.