The terms "small cell" and "large cell" are merely descriptive terms for the appearance of the cancer cells under the microscope.

Examining and noting the characteristics of your cancer cells helps your doctor determine your type of cancer, where it began and how abnormal the cells are. When combined with tests to determine the size of the cancerous area and whether cancer has spread, this information helps determine:

• The likely course or outcome (prognosis) of the cancer
• The most effective treatment for a specific cancer

Common terms used to describe the appearance of cancer cells include:

• Clear cell. The inside of the cell appears clear. Examples include some kidney, ovarian and uterine cancers.
• Spindle cell. The cell is narrower at both ends than at the center. Examples include some breast, gastrointestinal, muscle or other soft tissue, and skin cancers.
• Large cell. The cell is larger than are normal cells. Examples include lung cancer and lymphoma.
• Small cell. The cell is smaller than are normal cells. An example is small cell lung cancer, prostate cancer, or neuroendocrine cancer of the pancreas.
• Squamous cell. The cell is flat in appearance. Examples include skin cancer or any other type of cancer that starts in the lining of some organs, such as a bronchus of a lung.
• Adenocarcinoma. The cell is glandlike in appearance. Examples include breast, prostate, lung, gastric and endometrial cancers.
• Anaplastic. This term describes cells that look very abnormal, so abnormal that it may be difficult to tell where these cells originated.
• Metaplastic. This term describes tumors made up of many different types of cells that appear different from one another.
• Poorly differentiated. This term means the cancer cells appear very abnormal. In normal tissue, cells become specialized depending on where they are, for example, breast cells look different from colon cells. If cells look very unlike normal cells, they are considered poorly differentiated.

Other factors that help classify a cancer include:

• Area of the body in which the cancer originated, such as the liver or breast. Cancers from certain organs may have a similar appearance.

  For example, the most common type of kidney cancer is classified as clear cell. On the other hand, breast cancer rarely has a clear cell appearance. So clear cells on a breast biopsy may indicate that the cancer didn't originate in the breast but spread there (metastasized) from another area of the body, such as a kidney.

• Type of tissue from which the cancer evolved, including carcinomas and sarcomas. 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.