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Carcinoma of Unknown Primary Treatment (PDQ®): Treatment - Patient Information [NCI] - General Information About Carcinoma of Unknown Primary

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If tests show there may be cancer, a biopsy is done.

A biopsy is the removal of cells or tissues so they can be viewed under a microscope by a pathologist. The pathologist views the tissue under a microscope to look for cancer cells and to find out the type of cancer. The type of biopsy that is done depends on the part of the body being tested for cancer. One of the following types of biopsies may be used:

  • Excisional biopsy: The removal of an entire lump of tissue.
  • Incisional biopsy: The removal of part of a lump or a sample of tissue.
  • Core biopsy: The removal of tissue using a wide needle.
  • Fine-needle aspiration (FNA) biopsy: The removal tissue or fluid using a thin needle.

If cancer is found, one or more of the following laboratory tests may be used to study the tissue samples and find out the type of cancer:

  • Histologic study: A laboratory test in which stains are added to a sample of cancer cells or tissue and viewed under a microscope to look for certain changes in the cells. Certain changes in the cells are linked to certain types of cancer.
  • Immunohistochemistry study: A laboratory test in which dyes or enzymes are added to a sample of cancer cells or tissue to test for certain antigens (proteins that stimulate the body's immune response).
  • Reverse transcription–polymerase chain reaction (RT-PCR) test: A laboratory test in which cells in a sample of tissue are studied using chemicals to look for certain changes in the genes.
  • Cytogenetic analysis: A laboratory test in which cells in a sample of tissue are viewed under a microscope to look for certain changes in the chromosomes. Changes in certain chromosomes are linked to certain types of cancer.
  • Light and electron microscopy: A laboratory test in which cells in a sample of tissue are viewed under regular and high-powered microscopes to look for certain changes in the cells.

When the type of cancer cells or tissue removed is different from the type of cancer cells expected to be found, a diagnosis of CUP may be made.

The cells in the body have a certain look that depends on the type of tissue they come from. For example, a sample of cancer tissue taken from the breast is expected to be made up of breast cells. However, if the sample of tissue is a different type of cell (not made up of breast cells), it is likely that the cells have spread to the breast from another part of the body. In order to plan treatment, doctors first try to find the primary cancer (the cancer that first formed).

Tests and procedures used to find the primary cancer depend on where the cancer has spread.

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WebMD Public Information from the National Cancer Institute

Last Updated: February 25, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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