How Is a Cytology Test Done?

Cytology testing is done to screen for and diagnose diseases, including cancer, by looking at cells under a microscope.

What is a cytology test?

Diagnosing diseases by looking at single cells and small clusters of cells under a microscope is called cytology or cytopathology testing. It’s an important part of diagnosing some types of cancer.

Cytology tests differ from biopsies because they only use a few cells, rather than a larger tissue sample. Compared with a biopsy, collecting a cytology sample is often:

• Easier to do
• Less likely to have serious complications
• Less painful
• Less costly

Compared with a biopsy, cytology tests may provide less detailed information. They cannot give information about how cells are arranged or how deeply a tumor might have grown into the tissue. However, they are often just as useful.

Cytology tests are used for two main purposes:

• Screening cytology tests can help find cancer before symptoms appear.
• Diagnostic cytology tests are used to test for disease when a person has signs or symptoms. They can also help evaluate abnormal screening results and often assist in classifying disease.

If cytology results suggest cancer, a biopsy is often done to confirm the diagnosis before treatment begins.

How are cytology samples collected?

Cytology samples can be collected in multiple ways to test for cancer:

How long are cytology samples kept?

Processed cytology samples can be stored on slides or within paraffin (wax) blocks.

Why keeping samples can be helpful

Processed samples are usually kept for a set amount of time, which allows them to be sent to another doctor or lab for a second opinion. This process, called a cytopathology review, involves another doctor examining the sample to confirm or suggest a different diagnosis.

Keeping samples can also help if a new cancer occurs years later. Original and new slides can be compared to help determine if the cancer has come back (recurrence) or if it is new. Additional tests, like special stains on the original cells, might also be helpful.

Legal requirements

Clinical labs are regulated and certified based on a federal law called CLIA (Clinical Laboratory Improvement Amendments). To be CLIA accredited, labs must keep cytology samples for a minimum amount of time. For instance, CLIA says that labs must keep:

• Cytology slides for at least 5 years
• Paraffin blocks for at least 2 years

Some states have their own laws that require labs to keep cytology samples longer than the time specified by CLIA. And some labs have policies for keeping samples even longer than required by federal or state laws.

If you would like to know if the lab you go to is CLIA certified, you can ask the lab staff. Or if you have questions or concerns, you can reach out to your state’s CLIA agency.