Clinical, histopathological and immunophenotypical findings in five horses with cutaneous malignant lymphoma.

The researchers conducted a study to understand the clinical, histopathological, and immunophenotypical observations in five horses suffering from skin-based malignant lymphoma. The study suggests that these lymphomas are of T-cell origin and indicates potential usefulness of flow-cytometric analysis for faster tumor identification.

Clinical Observations and Histopathological Findings

• The study followed five horses with malignant lymphoma (ML), a cancer that affects the lymphocytes, a type of white blood cell that plays a crucial role in the immune system. These were non-epidermotropic (not impacting the epidermis) cutaneous (skin) MLs.
• The average survival time since the first appearance of subcutaneous nodules was approximately 3.8 years, with individual survival times ranging between 2 to 5 years.
• On a cellular level, the cutaneous ML followed a pleiomorphic structure and was composed of a variety of cells, including large reticulo-endothelial cells, different sizes of lymphoid cells, and small lymphoid cells.

Immunohistochemical and Flow-Cytometric Findings

• Immunohistochemistry (IHC), a technique that helps identify cells in tissues, revealed that lymphoid cells were CD3 positive (meaning they were T-lymphocytes) and negative for B-lymphocyte markers CD21, kappa, and lambda immunoglobulin light chains.
• Even though common blood examination revealed no abnormalities in the horses with cutaneous ML, changes were evident when their peripheral blood lymphocytes were analyzed using flow cytometry, a technique assisting detailed characterization of cells.
• In comparison to healthy horses, affected horses had a lower percentage of cells in the lymphocyte category. Additionally, three of the five horses showed an increase in the CD4 positive cells in the monocyte category.
• Flow-cytometric analysis of tumor cells collected through fine needle aspiration (FNA) – a procedure to extract cells for examination – suggested that the cutaneous MLs mainly consisted of CD4 and CD8 positive T-lymphocytes.

Comparison and Conclusion

• The data obtained from this research was compared to that of a monomorphic multicentric T- and B-cell lymphoma. It showed that the results from Immunohistochemistry and flow-cytometry were mostly, but not completely, similar.
• Overall, the research suggests that the cutaneous non-epidermotropic MLs in horses have a T-cell origin, opposing the common belief of B-cell origin. Additionally, the study hints towards the possibility of using FNA-based flow-cytometric analysis as a quicker method for identifying tumors, given its accuracy can be improved.