What is Cancer: Signs, Symptoms, & Common Types

| Patient Education

Cancer is a disease where some of the body’s cells grow out of control and spread to other parts of the body, creating masses called tumors. This can take place almost anywhere in the body, which is constantly generating new cells to function. There are more than 100 different types of cancer as a result, but all of them start with this basic defect in the body's process of reproducing cells

What Are the Symptoms of Cancer?

Cancer symptoms vary widely by individual and type of cancer. However, several symptoms are common. If you are experiencing any of the following, you should contact your healthcare provider:

  • A new, unusual lump

  • Chronic soreness

  • Difficulty swallowing

  • Hoarseness

  • A mole that changed color or shape

What Are the Stages of Cancer?

Most cancers develop in four stages. Knowing the characteristics of each stage is important for patients and their families

Stage 0

There is technically no cancer at stage 0, but there are abnormal cells that could become cancer. This is also called carcinoma in situ.

Stage 1

The cancer is small and only in one area of the body. Stage I is often called early-stage cancer.

Stage 2 & 3

The cancer has grown more deeply into surrounding tissue or lymph nodes, but no further.

Stage 4

The cancer has spread to other regions of the body. Stage 4 is also called advanced or metastatic cancer and is the most severe stage.

What Causes Cancer?

There is not a single cause of cancer. Scientists think that a combination of genetic, environmental, or lifestyle factors lead to cancer. Some cancers have been linked with certain risk factors, such as smoking nicotine products, exposure to toxic chemicals, or genetic disorders. Different types of cancer often have different causes. Learn more about the most common types of cancer below.

Common Types of Cancer

As mentioned above, there are over 100 different types of cancer. But some are more common than others. In general, cancers are named according to the area(s) of the body they infect. Here's an overview of some of the most pervasive types of cancer.

Lung Cancer

Cancer that forms in the tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small cell lung cancer. These types are diagnosed based on how the cells look under a microscope

Breast Cancer

Cancer that forms in tissues of the breast. The most common type of breast cancer is ductal carcinoma, which begins in the lining of the milk ducts (thin tubes that carry milk from the lobules of the breast to the nipple)

Colon Cancer

Cancer that forms in the tissues of the colon (the longest part of the large intestine). Most colon cancers are adenocarcinomas, cancers that begin in cells that make and release mucus and other fluids

Prostate Cancer

Cancer that forms in tissues of the prostate (a gland in the male reproductive system found below the bladder and in front of the rectum). Prostate cancer usually occurs in older men


Cancer that starts in blood-forming tissue, such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the bloodstream

Skin Cancer

Cancer that forms in the tissues of the skin. There are several types of skin cancer. Skin cancer that forms in melanocytes (skin cells that make pigment), for example, is called melanoma

*Cancer definitions provided by the National Cancer Institute.