Histopathological patterns and immunophenotyping of feline lymphomas and incidence in Metropolitan Bangkok, Thailand.

Abstract

Background and aim: Feline lymphomas are categorized based on the location of tumor cells, with anatomical classifications including alimentary, mediastinal, multicentric, and extranodal forms. Accurate diagnosis and classification of feline lymphoma are paramount for enhancing treatment and prognosis. T-cell lymphomas are CD3 positive, while B-cell lymphomas exhibit positive forCD20, CD79α, and paired box 5 (PAX5). The aims of this study were (1) to classify feline lymphoma in each anatomical subtype using the World Health Organization (WHO) classification to provide information on epidemiological findings; (2) to investigate the expression and detection of B-cell lymphoma, various antibodies will be used, with the addition of PAX5, for clearer results; and (3) to gather more extensive information about feline lymphoma in Thailand, particularly in the Bangkok area.

Materials and methods: From 2011 to 2023, 86 sample tissues were submitted for routine pathological examination at the Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University. Immunohistochemistry (IHC) was performed to detect an immunophenotype of PAX5, CD79α, CD20 (B-cell lineage), and CD3 (T-cell lineage). Eighty-six formalin-fixed, paraffin-embedded lymphoma tissues were prepared on silane-coated slides. After IHC, all cases were classified according to the WHO classification.

Results: The most common form of lymphoma in this study was extranodal lymphoma at 37.2% (32/86), followed by multicentric lymphoma at 31.3% (27/74), mediastinal lymphoma at 17.4% (15/86), and alimentary lymphoma at 14% (12/86). Most extranodal lymphoma cases were in the nasal region. From the anatomical form, multicentric and extranodal lymphomas were predominantly diffuse large B-cell high-grade, while mediastinal lymphomas were small low-grade B-cell lymphomas. Alimentary lymphomas occur in various types, with most being the B-cell type.

Conclusion: This study indicates that extranodal lymphoma and extranodal lymphoma are the most frequent presentations found in cats in Bangkok. Mediastinal and alimentary lymphomas still occur. The utilization of various B-cell markers in combination could aid pathologists in distinguishing between various stages of B-cell maturation, assessing tumor cell heterogeneity, and determining the phenotype in scenarios where there is a loss of common B-cell markers diffuse large B-cell lymphomas is the most prevalent subtype of feline lymphoma. Significantly, relying solely on immunochemistry with one parameter may not be sufficient for a definitive diagnosis of B-cell lymphoma, as another parameter may also be necessary.