Cancer is not a single disease but a collection of over 100 diseases, each characterized by the uncontrolled growth of abnormal cells. These diseases are broadly classified based on the origin of the cancer – the types of cells and tissues initially affected. For instance, lung cancer begins in the lungs, while brain cancer originates in the brain. Furthermore, cancers can be categorized by the specific type of cell from which they develop, such as epithelial cells or squamous cells. Understanding these classifications is crucial for diagnosis, treatment, and research.
To explore specific cancers, you can utilize resources that categorize cancers by their location in the body or through an A to Z list of cancer types. Information is also available for specialized categories like childhood cancers and cancers affecting adolescents and young adults.
Here’s a breakdown of the major categories of cancers, classified by their cellular origins:
Major Categories of Cancer Based on Cell Type
Carcinoma
Carcinomas represent the most prevalent type of cancer. They originate in epithelial cells, which line the surfaces of the body, both internal and external. Epithelial cells are diverse and often appear column-shaped under a microscope.
Carcinomas are further subcategorized based on the specific epithelial cell type:
- Adenocarcinoma: This type develops in epithelial cells that produce fluids or mucus. These tissues are often referred to as glandular tissues. Common examples include adenocarcinomas of the breast, colon, and prostate.
- Basal Cell Carcinoma: Originating in the basal layer, the lowest layer of the epidermis (outer skin layer), this is a common type of skin cancer.
- Squamous Cell Carcinoma: This cancer arises from squamous cells, epithelial cells located just beneath the skin’s outer surface. Squamous cells, resembling fish scales under a microscope, also line organs such as the stomach, intestines, lungs, bladder, and kidneys. Squamous cell carcinomas are sometimes referred to as epidermoid carcinomas.
- Transitional Cell Carcinoma: Developing in the transitional epithelium, or urothelium, this tissue is composed of multiple layers of epithelial cells capable of stretching. It lines the bladder, ureters, parts of the kidneys (renal pelvis), and certain other organs. Transitional cell carcinomas are found in some cancers of the bladder, ureters, and kidneys.
Sarcoma
Sarcomas are cancers that develop in the bones and soft tissues of the body. Soft tissues include muscle, fat, blood vessels, lymph vessels, and fibrous tissue like tendons and ligaments.
- Osteosarcoma is the most frequently diagnosed cancer of the bone.
- Common types of soft tissue sarcoma include leiomyosarcoma, Kaposi sarcoma, malignant fibrous histiocytoma, liposarcoma, and dermatofibrosarcoma protuberans.
Further information can be found on resources dedicated to soft tissue sarcoma.
Leukemia
Leukemias are cancers that originate in the blood-forming tissue of the bone marrow. Unlike many cancers, leukemias do not form solid tumors. Instead, they are characterized by a rapid increase in abnormal white blood cells (leukemia cells and leukemic blast cells) within the blood and bone marrow. This proliferation crowds out normal blood cells, potentially leading to complications such as reduced oxygen supply to tissues, bleeding issues, and increased susceptibility to infections.
Leukemias are categorized based on their progression rate (acute or chronic) and the type of blood cell affected (lymphoblastic or myeloid). Acute leukemias progress rapidly, while chronic forms develop more slowly.
Detailed information is available on resources focusing on leukemia.
Lymphoma
Lymphoma is a cancer that begins in lymphocytes, a type of white blood cell crucial to the immune system (including T cells and B cells). In lymphoma, abnormal lymphocytes accumulate in lymph nodes, lymph vessels, and other organs throughout the body.
There are two primary types of lymphoma:
- Hodgkin Lymphoma: Characterized by the presence of abnormal lymphocytes called Reed-Sternberg cells, which typically originate from B cells.
- Non-Hodgkin Lymphoma: A broad group encompassing various cancers that start in lymphocytes. These cancers can exhibit rapid or slow growth and can develop from either B cells or T cells.
More comprehensive information can be found on resources dedicated to lymphoma.
Multiple Myeloma
Multiple myeloma is a cancer that starts in plasma cells, another type of immune cell. Abnormal plasma cells, known as myeloma cells, accumulate in the bone marrow and form tumors within bones throughout the body. Multiple myeloma is also referred to as plasma cell myeloma or Kahler disease.
Detailed information is available on resources focusing on multiple myeloma and other plasma cell neoplasms.
Melanoma
Melanoma is a cancer that originates in melanocytes, specialized cells responsible for producing melanin, the pigment that gives skin its color. While most melanomas occur on the skin, they can also develop in other pigmented tissues, such as the eye.
Further information is available on resources dedicated to skin cancer and intraocular melanoma.
Brain and Spinal Cord Tumors
Brain and spinal cord tumors encompass a variety of types, named according to the cell type of origin and the tumor’s initial location within the central nervous system. For example, an astrocytic tumor originates in astrocytes, star-shaped brain cells that support nerve cell health. Brain tumors can be benign (non-cancerous) or malignant (cancerous).
Detailed information can be found on resources dedicated to brain and spinal cord tumors.
Other Types of Tumors
Germ Cell Tumors
Germ cell tumors originate in the cells that develop into sperm or eggs. These tumors can occur in various body locations and can be either benign or malignant.
A list of germ cell tumors with links to further information is available in resources categorizing cancers by body location/system.
Neuroendocrine Tumors
Neuroendocrine tumors develop from cells that release hormones into the bloodstream in response to nervous system signals. These tumors may produce excessive hormone levels, leading to diverse symptoms. Neuroendocrine tumors can be benign or malignant.
A detailed definition of neuroendocrine tumors is available in dedicated resources.
Carcinoid Tumors
Carcinoid tumors are a subtype of neuroendocrine tumor. These slow-growing tumors are typically found in the gastrointestinal system, most commonly in the rectum and small intestine. Carcinoid tumors may spread to the liver or other body sites and can secrete substances like serotonin or prostaglandins, causing carcinoid syndrome.
Further information is available on resources dedicated to gastrointestinal neuroendocrine tumors.
In conclusion, understanding the diverse types of cancer and their classifications is fundamental to navigating cancer diagnosis, treatment, and research. Each category represents a unique set of diseases with distinct characteristics and requires specialized approaches.
