Cancer is not a single disease. Instead, it is a broad term used to describe a large group of diseases that can develop in almost any part of the body. Each type of cancer behaves differently, affects different tissues, and may be described in unique ways. Understanding the major types of cancer can help individuals and families better navigate cancer-related information and discussions.

According to the National Cancer Institute (NCI), cancer occurs when abnormal cells grow uncontrollably and may spread to other parts of the body. The way cancer develops and spreads depends largely on the type of cell where it begins.

This pillar article provides a comprehensive overview of the main types of cancer, organized by the type of cell or tissue involved. The purpose is education and awareness—not diagnosis or treatment guidance—so readers can better understand how cancers are classified and discussed.

How Cancers Are Classified

Cancers are commonly classified based on the type of cell or tissue in which they begin. This classification helps researchers, educators, and healthcare professionals describe cancer in a consistent way.

The World Health Organization (WHO) explains that cancer classification is essential for understanding how cancer behaves, how common it is, and how it spreads within the body.

Major cancer categories include:

• Carcinomas
• Sarcomas
• Leukemias
• Lymphomas
• Multiple myeloma
• Melanoma
• Brain and spinal cord tumors

Each category includes many specific cancer types, and no single category explains all cancers.

Carcinomas

Carcinomas are the most common type of cancer. They begin in epithelial cells, which are the cells that cover the inside and outside surfaces of the body.

According to the National Cancer Institute, epithelial cells are found in:

• The skin
• The lining of organs
• The lining of blood vessels

Because epithelial cells are present throughout the body, carcinomas can develop in many different organs.

Common Types of Carcinoma

Carcinomas are often named after the organ or tissue where they start. Examples include:

• Breast carcinoma
• Lung carcinoma
• Colorectal carcinoma
• Prostate carcinoma
• Pancreatic carcinoma

The American Cancer Society (ACS) notes that carcinomas account for the majority of cancer diagnoses worldwide.

Subtypes of Carcinoma

Carcinomas may also be classified by how the cancer cells look under a microscope. Common subtypes include:

• Adenocarcinoma – begins in gland-forming cells
• Squamous cell carcinoma – begins in flat epithelial cells
• Basal cell carcinoma – begins in basal cells of the skin

These subtypes help further describe cancer characteristics but do not change the basic definition of carcinoma.

Sarcomas

Sarcomas are cancers that begin in connective tissues. These tissues support, connect, or surround other structures in the body.

The National Cancer Institute explains that connective tissues include:

• Bones
• Muscles
• Fat
• Cartilage
• Blood vessels

Sarcomas are much less common than carcinomas, but they can occur at any age.

Examples of Sarcomas

• Osteosarcoma (bone)
• Leiomyosarcoma (smooth muscle)
• Liposarcoma (fat tissue)
• Angiosarcoma (blood vessels)

Because connective tissue is found throughout the body, sarcomas may develop in many locations.

Leukemia

Leukemia is a type of cancer that begins in blood-forming tissues, primarily the bone marrow. Unlike many other cancers, leukemia does not usually form a solid tumor. Instead, it affects the production and function of blood cells.

According to the National Cancer Institute (NCI), leukemia develops when abnormal blood cells grow uncontrollably and crowd out healthy blood cells in the bone marrow.

Because blood cells circulate throughout the body, leukemia is often described as a systemic cancer rather than a localized one.

Main Types of Leukemia

Leukemia is commonly classified based on how quickly it progresses and the type of blood cell involved.

• Acute leukemia – progresses rapidly
• Chronic leukemia – progresses more slowly
• Lymphocytic leukemia – affects lymphoid cells
• Myeloid leukemia – affects myeloid cells

The American Cancer Society (ACS) explains that combining these categories results in several major leukemia types, such as acute lymphocytic leukemia (ALL) and chronic myeloid leukemia (CML).

Lymphoma

Lymphoma is a cancer that begins in the lymphatic system, which is part of the immune system. The lymphatic system includes lymph nodes, lymph vessels, the spleen, and other immune-related tissues.

According to the National Cancer Institute, lymphoma develops when lymphocytes (a type of white blood cell) grow abnormally and accumulate in lymph nodes or other tissues.

Hodgkin and Non-Hodgkin Lymphoma

Lymphomas are broadly divided into two main categories:

• Hodgkin lymphoma
• Non-Hodgkin lymphoma

The World Health Organization (WHO) notes that these categories are based on differences in how cancer cells appear and behave.

Non-Hodgkin lymphoma includes many subtypes that vary in how quickly they grow and where they develop in the body.

Multiple Myeloma

Multiple myeloma is a cancer that begins in plasma cells, which are a type of white blood cell found in the bone marrow. Plasma cells play a role in producing antibodies.

According to the National Cancer Institute, multiple myeloma occurs when abnormal plasma cells multiply and interfere with the production of healthy blood cells.

Because plasma cells are located in the bone marrow, multiple myeloma affects multiple areas of the body rather than forming a single tumor.

How Multiple Myeloma Differs From Other Blood Cancers

While leukemia and lymphoma affect different types of blood cells, multiple myeloma specifically involves plasma cells. This distinction helps explain differences in how these cancers are discussed and classified.

The American Cancer Society emphasizes that multiple myeloma is considered both a blood cancer and a bone marrow cancer.

Blood Cancers vs. Solid Tumors

One key distinction in cancer classification is the difference between blood cancers and solid tumors.

Blood cancers, such as leukemia, lymphoma, and multiple myeloma, involve cells that circulate throughout the body or are produced in the bone marrow.

Solid tumors develop as masses of tissue in specific organs or structures, such as the lungs, breast, or colon.

The Centers for Disease Control and Prevention (CDC) explains that this distinction affects how cancers are detected, monitored, and discussed.

Understanding this difference helps clarify why some cancers are found through imaging or physical exams, while others are identified through blood or laboratory testing.

Why Classification Matters

Classifying cancers by type helps support research, education, and public health efforts. It allows experts to study patterns, compare outcomes, and develop targeted educational resources.

For individuals and families, understanding cancer types helps make sense of information without requiring medical expertise.

As the UK National Health Service (NHS) notes, learning how cancers are grouped can reduce confusion and improve communication.

Melanoma

Melanoma is a type of cancer that begins in melanocytes, the cells responsible for producing melanin, which gives skin its color. While melanoma most commonly develops on the skin, it can also occur in the eyes or other parts of the body that contain melanocytes.

According to the National Cancer Institute (NCI), melanoma is less common than other skin cancers but is more likely to spread if not detected early.

Melanoma may appear as a new spot on the skin or a change in an existing mole. Because the skin is visible, melanoma is sometimes identified earlier than cancers that develop inside the body.

How Melanoma Differs From Other Skin Cancers

Not all skin cancers are melanoma. Other common skin cancers, such as basal cell carcinoma and squamous cell carcinoma, develop from different types of skin cells.

The American Cancer Society (ACS) explains that melanoma behaves differently from other skin cancers and is classified separately because of its higher potential to spread.

Brain and Spinal Cord Tumors

Brain and spinal cord tumors are cancers that begin in the central nervous system. These cancers are often grouped together because of their location and the types of cells involved.

According to the National Cancer Institute, tumors in the brain and spinal cord can be either cancerous or non-cancerous, but both can cause serious health effects due to pressure on surrounding tissues.

Unlike many other cancers, brain tumors rarely spread outside the central nervous system. Instead, their impact is often related to where they are located.

Types of Brain Tumors

Brain tumors may begin in different types of cells, including:

• Glial cells (gliomas)
• Astrocytes (astrocytomas)
• Oligodendrocytes (oligodendrogliomas)

The World Health Organization (WHO) provides detailed classification systems for tumors of the central nervous system based on cell type and behavior.

Neuroendocrine Tumors

Neuroendocrine tumors (NETs) develop from neuroendocrine cells, which have traits of both nerve cells and hormone-producing cells. These cells are found throughout the body.

According to the National Cancer Institute, neuroendocrine tumors can develop in organs such as the lungs, pancreas, and digestive tract.

Neuroendocrine tumors may grow slowly or more quickly, depending on the type. Because they can produce hormones, some NETs cause symptoms related to hormone release.

Why Neuroendocrine Tumors Are Considered a Separate Category

Neuroendocrine tumors are classified separately because of their unique cellular features and behaviors.

The American Cancer Society notes that NETs do not fit neatly into traditional carcinoma or sarcoma categories.

Rare and Less Common Cancer Types

In addition to major cancer categories, there are many rare and less common cancers. While each affects a smaller number of people, together they represent an important part of cancer awareness.

Examples of rare cancers include:

• Mesothelioma
• Thymoma
• Adrenal cancer
• Soft tissue sarcomas

The National Cancer Institute emphasizes that rare cancers may be harder to study due to smaller patient populations.

The UK National Health Service (NHS) also highlights the importance of awareness and specialized care for rare cancer types.

Why Some Cancers Are Considered Rare

Cancers are often classified as rare based on how frequently they occur in the population. A cancer may be considered rare even if it is serious or aggressive.

Factors that influence rarity include:

• The type of cell involved
• Genetic characteristics
• Environmental or occupational exposures

Understanding rare cancers helps support inclusive cancer education and research.

Childhood Cancers

Childhood cancers are cancers that occur in children and adolescents. These cancers are different from adult cancers in terms of the types that develop, how they grow, and how they are classified.

According to the National Cancer Institute (NCI), childhood cancers often begin in developing tissues, such as bone marrow, brain, or nervous system cells.

Common types of childhood cancer include:

• Leukemia
• Brain and spinal cord tumors
• Neuroblastoma
• Wilms tumor
• Lymphoma

The World Health Organization (WHO) notes that childhood cancers are relatively rare compared to adult cancers but remain a leading cause of disease-related death in children worldwide.

Unlike many adult cancers, childhood cancers are generally not linked to lifestyle-related risk factors.

Cancers Grouped by Body System

In addition to classification by cell type, cancers are often discussed based on the body system or organ they affect. This approach helps individuals understand where cancer begins and which parts of the body may be involved.

Examples of cancer groupings by body system include:

• Respiratory system: lung cancer
• Digestive system: colorectal, stomach, liver cancers
• Reproductive system: prostate, ovarian, cervical cancers
• Urinary system: kidney, bladder cancers
• Nervous system: brain and spinal cord tumors

The Centers for Disease Control and Prevention (CDC) explains that grouping cancers by body system supports population-level tracking and education.

These groupings overlap with cell-based classifications, which is why a single cancer may fit into more than one category.

Why Cancer Classification Systems Overlap

Cancer classification systems are designed to describe different aspects of cancer. As a result, overlap is common and expected.

A single cancer may be described by:

• The type of cell where it began
• The organ or body system involved
• Its stage and extent of spread
• Its genetic or molecular features

The National Cancer Institute emphasizes that these classifications work together to provide a more complete picture.

Understanding overlap helps reduce confusion when different terms are used to describe the same cancer.

Why Understanding Cancer Types Matters

Learning about the different types of cancer helps individuals and families better understand cancer-related information, research, and public health discussions.

Understanding cancer types supports:

• Clearer communication
• Reduced misinformation
• Greater confidence when reading or hearing cancer-related content

As the American Cancer Society notes, education about cancer types helps people understand that cancer is not one disease, but many.

Summary

Cancer includes a wide range of diseases that begin in different cells, tissues, and organs. Major cancer types include carcinomas, sarcomas, blood cancers, melanoma, brain tumors, and many rare forms.

Understanding how cancers are classified helps individuals and families better interpret cancer-related information, reduces confusion, and supports informed awareness.

Disclaimer: This content is for general education only and is not medical advice. Always consult a licensed healthcare professional for guidance about your health.