By Dr Ananya Mandal, MD
Carcinomas are cancers or malignancies that begin in the epithelial tissues. Epithelial cells are the cells that line the entire surface of the body as well as the internal structures and cavities. Carcinomas may affect the breast, lung, prostate, and colon and are among the most common types of cancer in adults.
Carcinomas are rare among children before adolescence. Children are more affected by cancers that are not carcinomas such as leukemias, lymphomas and sarcomas.
How does carcinoma begin?
The body is made up of trillions of living cells. These cells grow, divide, and die in an orderly fashion. This process is tightly regulated and controlled by the DNA machinery within the cell. In a fetus, baby or a child, cells divide rapidly to allow for growth. After the person becomes an adult, most cells divide only to replace worn-out or dying cells or to repair injuries.
When cells of the body at a particular site start to grow out of control, they may become cancerous. Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells continue to grow and form new, abnormal cells. In addition, these cells can also invade other tissues, a property that normal cells do not possess.
DNA is in every cell and directs all of the cell's actions such as growth, death and protein synthesis. When DNA in a normal cell is damaged, the cell either repairs the damage or dies. In cancer cells, the damaged DNA is not repaired, and the cell does not die.
Instead, it gives rise to more of the abnormal cells containing abnormal DNA. These new cells all have the same defective DNA of the original cancer cell.
Classification of carcinomas
Carcinomas from different origins are classified into six broad subgroups:
Adrenocortical carcinoma which affect the adrenal glands
Thyroid carcinoma which affects the thyroid gland
Nasopharyngeal carcinoma which affects the nose and pharynx
Malignant melanoma which describes skin cancer
Skin carcinoma other than melanoma
Other carcinomas including those affecting the salivary gland, colon, appendix, lung and bronchus, cervix, and urinary bladder
Carcinoma-in-situ (CIS) is a pre-cancerous condition. Under the microscope, cells with CIS show some degree of change but the epithelial basement membrane is not breached.
Reviewed by Sally Robertson, BSc