There are six major categories of cancer, grouped by the type of cell or tissue where they start: carcinoma, sarcoma, leukemia, lymphoma, myeloma, and mixed types. Within those categories, hundreds of distinct cancers exist. Understanding the broad groups makes it easier to grasp how different cancers behave, where they grow, and why treatments vary so widely from one diagnosis to another.
Carcinoma: The Most Common Category
Carcinomas account for 80 to 90 percent of all cancer cases. They begin in epithelial cells, the tissue that lines your skin, organs, and internal passageways. Because epithelial tissue covers so much of the body, carcinomas can appear almost anywhere.
The two main subtypes are adenocarcinoma and squamous cell carcinoma. Adenocarcinoma starts in gland cells, which produce substances like mucus, saliva, and digestive fluids. Most breast cancers, colon cancers, prostate cancers, and lung cancers are adenocarcinomas. Squamous cell carcinoma starts in the thin, flat cells that line surfaces like the skin, throat, and esophagus. In some organs, like the esophagus, either subtype can develop depending partly on geography and risk factors.
Basal cell carcinoma, the most common skin cancer, is another carcinoma subtype. It grows slowly and rarely spreads to distant parts of the body, which is why it carries a very different prognosis than, say, a lung carcinoma.
Sarcoma: Cancer in Bone and Soft Tissue
Sarcomas start in the body’s supportive and connective tissues: bones, cartilage, fat, muscle, blood vessels, tendons, and the tissue around joints. They split into two broad groups. Bone sarcomas, like osteosarcoma and Ewing’s sarcoma, originate in bone itself. Soft tissue sarcomas, like liposarcoma (from fat) and leiomyosarcoma (from smooth muscle), develop in the tissues that connect, support, or surround other structures.
Sarcomas are far less common than carcinomas. They make up a small fraction of adult cancer diagnoses but represent a larger share of childhood cancers. Because connective tissue exists throughout the body, sarcomas can appear in the leg, abdomen, chest wall, or virtually anywhere else.
Blood and Bone Marrow Cancers
Three major categories of cancer arise from blood-forming cells, and they differ mainly in where the abnormal cells accumulate.
Leukemia is sometimes called a “liquid cancer.” It develops in the bone marrow, where blood cells are produced, and the cancerous cells circulate through the bloodstream. Leukemia doesn’t form a solid tumor. There are several types, broadly split by how quickly they progress (acute or chronic) and which type of white blood cell is involved.
Lymphoma also starts in white blood cells, but unlike leukemia, the abnormal cells tend to cluster into solid masses in the lymphatic system, particularly the lymph nodes, spleen, tonsils, and thymus. The two main forms are Hodgkin lymphoma and non-Hodgkin lymphoma, which behave differently and respond to different treatments.
Myeloma originates in plasma cells, a specific type of white blood cell in the bone marrow that normally produces antibodies. When plasma cells become cancerous, they crowd out healthy blood cells and produce abnormal proteins that can damage the kidneys and bones. Multiple myeloma, the most common form, typically affects several areas of bone marrow at once.
How Cancers Are Named
Cancer names usually combine two pieces of information: where the cancer started and what cell type is involved. A “renal cell carcinoma” is a carcinoma (epithelial origin) that began in the kidney. An “osteosarcoma” is a sarcoma that started in bone cells. This naming system matters because a cancer is always defined by its origin, even if it spreads. Breast cancer that moves to the lungs is still breast cancer, not lung cancer, and it’s treated based on its original biology.
Beyond tissue type, cancers are increasingly classified by their molecular features. Two breast cancers that look identical under a microscope can have completely different genetic profiles, which means they respond to different drugs. Molecular profiling identifies specific markers on a tumor’s surface or mutations in its DNA, allowing doctors to match treatments more precisely to the biology driving that particular cancer.
The Most Common Cancers Worldwide
Globally in 2022, lung cancer was the most frequently diagnosed cancer, with 2.5 million new cases (12.4% of all new cancers). Female breast cancer ranked second at 2.3 million cases, followed by colorectal cancer at 1.9 million, prostate cancer at 1.5 million, and stomach cancer at about 970,000 cases.
The deadliest cancers don’t perfectly mirror the most common ones. Lung cancer caused 1.8 million deaths, nearly double the next highest. Colorectal cancer, liver cancer, breast cancer, and stomach cancer rounded out the top five for mortality. The gap between incidence and death rates reflects how much survival varies by type. For people diagnosed in 2017 in the United States, the overall five-year survival rate across all cancers was 72.5%. But that average hides enormous variation: prostate cancer had a 98% five-year survival rate, breast cancer 93.2%, and colorectal cancer 68.6%, while lung cancer survival was just 29.5%.
Childhood Cancers Are Different
Cancer in children is rare. An estimated 9,550 new cases will be diagnosed in U.S. children under 15 in 2025. The types that affect children look very different from adult cancers. The most common childhood cancers are leukemias, brain and central nervous system tumors, and lymphomas. Carcinomas, which dominate adult cancer statistics, are uncommon in children.
The reasons behind childhood cancer also differ. In adults, cancer typically reflects decades of accumulated genetic damage from aging and environmental exposures. In children, the mutations driving cancer are less well understood, partly because the disease is so uncommon and partly because it’s difficult to pinpoint what a child may have been exposed to during early development. Children’s bodies also respond differently to treatment than adult bodies do, which is why pediatric oncology is its own specialty with distinct treatment approaches.
Rare Cancers
Any cancer with fewer than 15 cases per 100,000 people per year is generally classified as rare. By that definition, most individual cancer types are actually rare, even though cancer as a whole is common. Sarcomas, myeloma, and many specific subtypes of carcinoma all fall below that threshold. Rare cancers can be harder to diagnose because doctors encounter them less often, and treatment options may be more limited since large clinical trials require enough patients to produce reliable results. If you’re diagnosed with a less common cancer, a specialized cancer center with experience in that specific type can make a meaningful difference in care.