Cell and tissue studies

Cells and tissues are analyzed in the lab to look for cancer. Samples may be collected from body fluids (such as urine or blood) or from organs.

There are many different ways to study cells and tissues. Sometimes the focus is on cell structures, while other times the focus is on genes inside the cells.

Cells and tissue samples can be removed from almost any part of the body, including:

• solid organs (such as the breasts, prostate or lungs)
• skin
• lymph nodes
• bone marrow
• blood
• other body fluids (such as urine, cerebrospinal fluid or fluid in the lungs or abdomen)

How a cell or tissue sample gets collected depends on the type of cancer suspected and the part of the body affected. The most common procedures are:

• tissue scrapings (such as a Pap test)
• urine samples
• blood samples
• a fine needle aspiration (FNA)
• a biopsy

The cells and tissue samples are sent to the lab so that a pathologist, or sometimes a cytologist, can look at them under a microscope.

Special lab techniques are used to prepare the samples so that cells and tissues can be seen under a microscope. These techniques allow the pathologist or cytologist to see very small details in cells.

Cytochemistry and histochemistry use stains to identify cell and tissue structures.

Immunohistochemistry and immunofluorescence use fluorescent antibodies that bind to specific antigens (proteins) on a cell to help identify it.

Flow cytometry uses a laser that can detect many fluorescent antibodies at the same time.

Pathologists can use microscopes to find:

• the types of cells that are in the sample and how abnormal they are in shape and size
• the hormone receptor status of individual cells (such as estrogen and progesterone receptors in breast tissue)
• tumour marker proteins (such as PSA)
• oncogenes (such as ERBB2, more commonly known as HER2)
• specific proteins that help find out the cell type or how much a cell has grown and developed
• changes in the way tumour suppressor genes work

They can also see different characteristics of the cells, such as:

• how the normal cells look
• how the cancer cells look compared to the normal cells (grading)
• the genes inside the cancer cells

Molecular genetic studies look for abnormalities in chromosomes (the part of a cell that holds genetic information) or in the DNA of cells. Two techniques that are commonly used are:

Fluorescent in situ hybridization (FISH) uses fluorescent dyes linked to pieces of DNA that only attach to specific parts of certain chromosomes. This helps the pathologist see extra copies of oncogenes that can develop in some cancers (such as HER2).

Polymerase chain reaction (PCR) is a very sensitive test for finding specific DNA sequences by making many copies of a particular section of a gene. PCR can find even a very small number of cancer cells in blood or tissue samples.

Molecular genetic studies are done to:

• diagnose some cancers like lymphoma, leukemia and soft tissue sarcoma
• predict a person’s outlook (prognosis)
• predict if the cancer is going to be aggressive or if it will respond to certain treatments
• see if the cancer is gone

The pathologist prepares a pathology report with the results of cell and tissue studies.

Your doctor will use this pathology report to decide whether further tests, procedures, follow-up care or treatments are needed.