According to the National Cancer Institute (NCI), there are more than 100 types of cancer. Cancer types are generally named after the organs or tissues where they originate. For example, lung cancer starts in the lungs, while brain cancer starts in the brain. Cancer is sometimes classified based on the specific type of cell it develops from, such as epithelial or squamous cells.
Experts categorize some types of cancer by the specific cells where they begin.
Carcinoma
Carcinomas are the most common type of cancer. They originate in epithelial cells, which line the inside and outside surfaces of the body. There are several types of epithelial cells; under a microscope, they often appear as small columns.
Types of Carcinomas
Carcinomas are named based on the epithelial cell type in which they begin:
- Adenocarcinoma: Cancer that forms in epithelial cells that produce fluids or mucus. People often call this type of tissue glandular tissue. Most breast, colon, and prostate cancers are adenocarcinomas.
- Basal cell carcinoma: A type of skin cancer that forms in the basal layer of the epidermis (the skin’s outermost layer).
- Squamous cell carcinoma: Cancer originates in squamous cells, which are epithelial cells located just beneath the skin’s outer surface. Squamous cells also line many organs, such as the stomach, intestines, lungs, bladder, and kidneys. When viewed under a microscope, these cells appear flat, resembling fish scales. Some people call squamous cell carcinomas “epidermoid carcinomas.”.
- Transitional cell carcinoma: Cancer that begins in transitional epithelium, a tissue with multiple layers of epithelial cells that can expand and contract. This type of epithelium is found in the bladder, ureters, and renal pelvis (part of the kidney). Some bladder, ureter, and kidney cancers are transitional cell carcinomas.
Sarcoma
Sarcomas are cancers that develop in the bones and soft tissues, such as muscles, fat, blood vessels, lymphatic vessels, and fibrous tissue (tendons and ligaments).
- Osteosarcoma is the most common type of bone cancer.
Leukemia
Leukemias are cancers that begin in the bone marrow and do not form solid tumors. Instead, abnormal white blood cells (leukemic cells and leukemic blasts) accumulate in the blood and bone marrow. This excessive growth of abnormal cells interferes with the body’s ability to transport oxygen, control bleeding, and fight infections.
Lymphoma
Lymphoma is a type of cancer originating in lymphocytes (T cells or B cells), white blood cells that are part of the immune system. In lymphoma, abnormal lymphocytes build up in lymph nodes, lymphatic vessels, and other organs.
There are two main types of lymphoma:
- Hodgkin lymphoma is a disease characterized by Reed-Sternberg cells that usually originate from B cells.
- Non-Hodgkin lymphoma is a broad category of lymphomas that develop from B or T cells. These cancers can be either fast-growing or slow-growing.
Multiple Myeloma
Multiple myeloma is a cancer that begins in plasma cells, a type of immune cell. Abnormal plasma cells (myeloma cells) accumulate in the bone marrow, forming tumors throughout the bones. Multiple myeloma is also known as plasma cell myeloma or Kahler’s disease.
Melanoma
Melanoma is a type of cancer originating in melanocytes, the specialized cells that produce melanin, the pigment responsible for skin color. Most melanomas develop on the skin but can also appear in pigmented tissues such as the eye.
Brain and Spinal Cord Tumors
Many types of tumors develop in the brain and spinal cord. These tumors are named after the type of cell they originate from and the specific location within the central nervous system (CNS).
For example:
- Astrocytomas originate in astrocytes, star-shaped brain cells that help maintain healthy neurons.
Brain tumors can be benign (non-cancerous) or malignant (cancerous).
Other Types of Tumors
Germ Cell Tumors
Germ cell tumors develop from cells that later become sperm or eggs. These tumors can form anywhere in the body and may be benign or malignant.
Neuroendocrine Tumors
Neuroendocrine tumors arise from cells that release hormones into the bloodstream in response to nervous system signals. These tumors sometimes produce excess hormones, leading to various symptoms. Neuroendocrine tumors can be benign or malignant.
Carcinoid Tumors
Carcinoid tumors are a slow-growing type of neuroendocrine tumor. They are most commonly found in the digestive tract, particularly in the rectum and small intestine. Some carcinoid tumors spread to the liver or other parts of the body and may secrete substances such as serotonin and prostaglandins, causing a condition known as carcinoid syndrome.
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