Biopsy and Cytology Tests

IHC uses lab-made antibodies (immune system proteins) to detect specific proteins, called antigens, in cells. Each antibody binds only to its specific antigen, and a chemical reaction causes a color change that pathologists can see under a microscope.

IHC is useful for several reasons:

• Identifying the type of cancer. It can help determine where a cancer started. For example, if cancer cells are found in a lymph node, IHC can show whether the cancer began in the lymph node or has spread from another part of the body, which can help guide treatment.
• Finding hard-to-see cancer cells. IHC can highlight small number of cancer cells, which can help detect cancer in lymph nodes or other tissues.
• Guiding treatment. IHC can reveal if cancer cells have certain proteins, helps predict which therapies are likely to work. For example, breast cancer cells with hormone receptors may respond to hormone therapy, and cells with high HER2 levels may respond to HER2-targeted drugs.

Doctors often test multiple antibodies to confirm the cancer type. By combining IHC results with how the cells look under a microscope and where they are in the body, pathologists can provide detailed information that helps guide diagnosis, treatment, and outlook.

Flow cytometry is a lab test often used on samples from blood, bone marrow, or lymph nodes. It can identify the immunophenotype of the cells, which is the pattern of antigens in and on cells. It can help doctors identify the exact type of leukemia, lymphoma, or noncancerous disease a person has.

In this test, cells are treated with special antibodies that attach to certain antigens. These antibodies are linked to fluorescent chemicals that give off light when exposed to a laser beam, which can be measured by a machine.

 Flow cytometry can also measure how much DNA is in cancer cells (ploidy):

• Diploid cells have a normal amount of DNA.
• Aneuploid cells have an abnormal amount of DNA. In many cancers, aneuploid tumors tend to grow and spread faster.

The test can also measure the S-phase fraction, which shows how many cells are actively dividing. A higher percentage usually means the cancer is growing more quickly and may be more aggressive.

Image cytometry uses special dyes that attach to DNA to measure how much DNA is in cancer cells.

This test looks at cells on a microscope slide. A digital camera and computer analyze the images to measure DNA levels. Like flow cytometry, image cytometry can also determine the ploidy of cancer cells.

Unlike a standard microscope that uses light, an electron microscope uses beams of electrons and can magnify specimens about 1,000 times more than a light microscope. This level of detail is usually not needed to tell if a cell is cancerous, but it can show tiny details that help identify the exact type of cancer.

For example, some melanoma skin cancers can look like other types of cancer under a light microscope. Most of the time, these melanomas can be recognized by certain IHC stains. But if those tests are unclear, an electron microscope can be used to identify tiny structures inside melanoma cells called melanosomes.

This helps diagnose the type of cancer and might help in choosing the best treatment plan.

Some cancers contain cells with one or more abnormal chromosomes (long strands of DNA that carry genes). Finding these changes can help diagnose certain cancers, especially leukemias, lymphomas, and sarcomas.

For testing with cytogenetics, cancer cells are grown in a lab for about 2 weeks before the chromosomes can be looked at under the microscope. Then, the cells are ‘frozen,’ and the chromosomes are evaluated under a microscope. Because of this, it usually takes at least this long to get results.

If the cancer type is known, cytogenetics can sometimes help predict a person’s prognosis and which treatments are more likely to be helpful.

Normal human cells have 46 chromosomes. Common chromosome changes include:

• Translocation, where part of one chromosome breaks off and attaches to another.
• Inversion, where a piece of a chromosome is flipped backward.
• Deletion, where part of a chromosome is missing.
• Duplication, where extra copies of part of a chromosome are present.
• Gain or loss of a whole chromosome.

FISH is a lab test used to look for chromosome changes in cancer cells. It can find most changes seen with standard cytogenetic tests, as well as some that are too small to be seen under a regular microscope.

FISH uses special fluorescent dyes that attach to specific parts of chromosomes. This helps find changes like translocations, which can help classify some kinds of leukemia.

FISH can also show if there are extra copies of certain genes. For example, it can show when there are too many copies of the HER2 gene, known as HER2 amplification or HER2 overexpression. This helps doctors decide if medicines that target HER2 might be useful.

FISH results are usually ready within a few days.

This is a very sensitive test that looks for specific DNA changes linked to certain cancers. It works by making many copies of a DNA segment from a sample, even when only tiny amounts are present.

RT-PCR detects very small amounts of RNA, a substance related to DNA that’s needed for cells to make proteins.

It can find small numbers of cancer cells in blood or tissue samples, which might indicate that the cancer might come back.

RT-PCR can measure levels of several RNAs at the same time. This can help doctors predict how likely a cancer might be to grow and spread and whether it might respond to certain treatments.

These tests measure the activity of many genes in a tumor at the same time. The pattern of active (expressed) genes can help predict a person’s prognosis (outlook) and guide treatment options.

For example, in some early-stage breast cancers, this testing can show how likely it is that the cancer will come back after surgery and, possibly, radiation. This can help determine if chemotherapy is needed.

Gene expression profiling can also help when a cancer is found in different parts of the body, but doctors aren’t sure where it started (cancer of unknown primary or CUP). Comparing the tumor’s gene activity to known cancers may help identify where it began, although results are not always exact.

DNA sequencing looks at the exact order of DNA to find gene changes (mutations) in cancer cells.

In the past, this testing was used mainly to find inherited gene mutations that increase cancer risk. Now, newer methods such as next generation sequencing (NGS) can look for gene changes in cancer cells. This helps predict which targeted therapies are most likely to work.

Some tests look at only a few genes, while others analyze many of the genes in cancer cells. Sometimes, sequencing finds an unexpected gene change that allows for more treatment options.