|Micrograph of a lung primary small cell carcinoma, a type of carcinoma. The clustered cancerous cells consist primarily of nucleus (purple); they have only a scant rim of cytoplasm. The surrounding pale staining, discoid cells are red blood cells. Cytopathology specimen. Field stain.|
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. It is from the Greek: καρκίνωμα, romanized: karkinoma, lit. 'sore, ulcer, cancer' (itself derived from karkinos meaning crab).