Oncology Update: Flow Cytometry and Immunocytochemistry
Central Toronto Veterinary Referral Clinic
Kevin Finora DVM, Diplomate ACVIM (Oncology and Small Animal Internal Medicine)
Flow Cytometry and Immunocytochemistry
New techniques and methods of testing are always being developed to help general practioners and oncologists better and more easily identify, diagnose and characterize cancer. Often these new tests are developed in human medicine and are then translated, or trickle down, to veterinary medicine. In most cases the tests are developed in an academic setting and are then translated to clinical practice. This shift is the case with flow cytometry and immunocytochemistry.
Flow cytometry is a method for counting and evaluating cells. Creating a cell suspension, which is passed through a detection laser, rapid and simultaneous evaluation of cellular granularity and size occur. These characteristics are then used, via computer analysis, to help determine cell type. This method allows for the analysis of thousands of cells per second. In veterinary medicine, flow cytometry is most easily applied to fluid cytology samples, such as blood and bone marrow. However, cytology samples, suspended in buffer solution, can now just as easily and accurately be assessed as fluid samples. The initial usefulness of this technology has been to help diagnose diseases such as lymphoma, leukemia and thymoma.
An additional appliion of flow cytometry has been the development of immunocytochemistry. In this technique antibodies are mixed into the initial cellular suspension. These antibodies will bind with specific cells, such as B or T lymphocytes, mast cells or histiocytes. The antibody bound cells are detected by laser analysis, which easily facilitates a rapid and accurate diagnosis.
The application of immunocytochemistry has changed the way veterinary oncology is practiced, especially as it relates to immune system cancers, such as lymphoma, leukemia and mast cell tumours. In lymphoma, a major application is the determination of immunophenotype. Whether a lymphoma is B cell or T cell will have a significant impact on prognosis, and there is emerging evidence that T cell lymphoma may need to be treated differently. Indeed a new vaccine for T-cell lymphoma should be on the market in the next 12-18 months. In the past the only way to determine immunophenotype was to biopsy the lymph node for immunohistochemistry. Now an immunocytochemical test exists were cytology samples, taken by fine needle aspirate, can be analyzed. The flow analysis will confirm the diagnosis of lymphoma and determine the phenotype. This test is non-invasive, easy to complete and provides results rapidly and with accuracy. Flow cytometry is a test I commonly use in my practice.
An additional application of this test involves blood and bone marrow analysis. I have found this test to be especially useful in situations where a CBC returns with an indication of an elevated cell count but with an unclear interpretation of the blood smear, or simply a notation of “unclassified cells”. In these situations, I will submit an additional sample for analysis by flow cytomtery. In most cases this test will differentiate between inflammation and neoplasia and will characterize the type of leukemia that is present. In many cases flow analysis of the blood eliminates the need for bone marrow analysis. In situations where bone marrow cytology must be performed, samples can also be submitted for flow cytometry analysis to help provide a more in depth evaluation of the cells.
Flow cytometry is also the test of choice to differentiate, based on cytology samples alone, between lymphoma and thymoma. This distinction is especially essential as samples from a mediastinal mass can look identical under the microscope for each cancer. The treatments are so dramatically different that a definitive diagnosis is necessary. Flow cytometry is able to make that diagnosis when samples are suspended in buffer and submitted for analysis.
Flow cytometry and immunocytochemistry are tests, which have dramatically changed the ease with which the diagnosis of lymphoma and leukemia can be made. We are now able to gather information, which in past required biopsy or bone marrow aspirate, from cytology samples alone. This advancement has reduced morbidity, decreased cost and has proven to be very accurate.
Dr. Kevin Finora is a Board Certified Oncologist and Small Animal Internist who is part of the Healthcare Team at the Central Toronto Veterinary Referral Clinic. He is available for referrals and consultations Monday to Thursday (including Monday and Tuesday evenings). Please contact him with any oncology questions or concerns.
Posted by: Michael Goldstein, DVM, Diplomate ACVIM
Categorised as: Oncology
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