The terms "small cell" and "large cell" describe what cancer cells look like under a microscope.

Looking at the cancer cells and noting their size and shape gives your health care team helpful clues about your diagnosis. It helps your care team figure out the type of cancer you have and where the cancer began. A careful study of the cancer cells can also show how much the cells have changed compared to healthy cells.

Your health care team uses this information along with test results for the size and spread of the cancer to determine:

• The likely course or outcome of the cancer, which is also called the prognosis
• The best treatment for a certain cancer
• Whether surgery is an option

Terms used to describe what cancer cells look like under a microscope include:

• Clear cell. The inside of the cell seems clear. Cancers with clear cells include some kidney, ovarian and uterine cancers.
• Spindle cell. The cell is narrower at both ends than at the middle. Cancers with spindle cells include some breast, gastrointestinal, muscle or other soft tissue, and skin cancers.
• Large cell. The cell is larger than a typical cell. Cancers with large cells include some types of lung cancer and lymphoma.
• Small cell. The cell is smaller than a typical cell. Cancers with small cells include some types of lung cancer, prostate cancer and pancreatic neuroendocrine tumors. Sometimes these cancers are called small round cell cancers.
• Squamous cell. The cell looks flat. In the body, these cells are often arranged like tiles on a floor. Squamous cell cancers include some types of skin cancer and some types of cancer that start in the lining of organs, such as the bladder.
• Adenocarcinoma. The cell looks like a gland cell. Cancers with this type of cell include some types of breast, prostate, lung, gastric and endometrial cancers.
• Anaplastic. The cell looks very irregular. These cells may have an unusual size and may not resemble any typical cells. It may be hard to tell where these cells come from.
• Metaplastic. The cell has many different looks. Metaplastic cancers are made up of many different types of cells that look different from each other.
• Poorly differentiated. The cell appears very irregular. In typical tissue, cells in a certain area look different from cells in another area. For example, breast cells look different from colon cells. If cells look very unlike typical cells, they are considered poorly differentiated. In general, these cancers may be aggressive.

Other factors that help classify a cancer include:

• Part of the body in which the cancer started. Cancers are named for where they start. For example, if breast cancer spreads into the liver, it is still called breast cancer.
• Type of tissue from which the cancer started. Some terms used to describe cells can tell you about where the cancer started. For example, carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer of the bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.