Pathology dictionary

Plasma cells

What are plasma cells?

Plasma cells are part of the body’s immune system. They produce special proteins called antibodies (another word for antibody is immunoglobulin). Antibodies protect our body by sticking to bacteria and viruses, which makes them easier to remove from the body. Antibodies can also stick to abnormal cells or cells that have stopped functionally normally.

When examined under a microscope these cells are small round cells. The inside of the cell looks pink and the genetic material (the nucleus) is pushed to the side of the cell. Pathologists use the word eccentric to describe a nucleus on the side of a cell.

Pathologists use a special test called immunohistochemistry to help them see these cells under the microscope. When this test is performed plasma cells produce a protein called CD138. These cells also produce immunoglobulins called kappa and lambda.

Medical conditions associated with plasma cells

When examined under the microscope, groups of plasma cells can be seen during an infection or after an injury. Increased numbers of these cells can also be seen in certain medical conditions such as inflammatory bowel disease. Pathologists use the word plasmacytosis to describe the increased number of these cells seen in these conditions.


Some types of cancer are made up of plasma cells. The most common types of cancers are included in a group called plasma cell neoplasms. This group includes multiple myeloma.

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