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Diagnosis of mediastinal masses in dogs by flow cytometry
Susan Lana1, Susan Plaza, Kerri Hampe
1Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, USA.
Insights
Flow cytometry effectively distinguishes between canine mediastinal lymphoma and thymoma, even when cells appear similar. This method can reduce the need for invasive biopsies in diagnosing these common canine neoplasms.
Area of Science:
- Veterinary Medicine
- Immunology
- Oncology
Background:
- Mediastinal masses in dogs, particularly lymphoma and thymoma, can be challenging to diagnose via cytology due to similar cell morphology.
- Invasive biopsies are often required for definitive diagnosis when cytology is inconclusive.
Purpose of the Study:
- To evaluate the utility of flow cytometry in differentiating between canine mediastinal lymphoma and thymoma.
- To determine if flow cytometry can reduce the need for invasive biopsies.
Main Methods:
- Flow cytometry analysis of mediastinal mass aspirates from dogs.
- Quantification of B-cell and T-cell marker expression, including CD4 and CD8 co-expression.
- Analysis of light scatter properties for cell discrimination.
Main Results:
- Thymoma cases (n=6) consistently showed >=10% CD4+CD8+ lymphocytes, characteristic of thymocytes.
- Most lymphoma cases (6/7) exhibited <2% CD4+CD8+ lymphocytes.
- Flow cytometry, including light scatter, successfully distinguished between thymoma and lymphoma in all lymphocyte-rich cases (13/13).
Conclusions:
- Flow cytometry is a valuable tool for the definitive diagnosis of mediastinal masses in dogs.
- This technique allows for unambiguous identification of lymphoma and thymoma, potentially avoiding invasive procedures.
Background:
Biopsy of mediastinal masses can be invasive, but the procedure may be necessary if cytology of a mass aspirate is inconclusive. The 2 most common mediastinal masses, lymphoma and thymoma, may both be comprised of small lymphocytes. We investigated the ability of flow cytometry to distinguish between these 2 neoplasms.
Hypothesis:
Flow cytometry of mediastinal mass aspirates may provide a definitive diagnosis of thymoma or lymphoma, reducing the need for biopsy.
Animals:
Dogs with mediastinal masses presenting to the Veterinary Teaching Hospital/Animal Cancer Center were included in the study.
Methods:
Aspirates obtained over 2 years that met the inclusion criteria (i.e. sufficient viable cells and a definitive diagnosis by means other than flow cytometry) were analyzed by flow cytometry to determine the percentage of cells expressing B- and T-cell markers, and co-expressing CD4 and CD8.
Results:
All cases of thymoma (n = 6) consisted of > or = 10% lymphocytes coexpressing CD4 and CD8, a phenotype that is characteristic of thymocytes, whereas 6 of 7 lymphomas contained <2% CD4+CD8+ lymphocytes. The CD4+CD8+ lymphoma could be readily distinguished flow cytometrically from thymoma by light scatter properties. The phenotypes of the remaining lymphomas were CD4+ T cell (4), CD34+ (1) and B cell (1).
Conclusions:
Our studies demonstrate that flow cytometry is a useful tool for discriminating mediastinal masses. Lymphocyte-rich mediastinal masses could be unambiguously identified by flow cytometry in 13/13 cases.
