Immunophenotypic characterization and clinical outcome in cats with lymphocytosis. (6th November 2019)

• Record Type: Journal Article
• Authors: Rout, Emily D.; Labadie, Julia D.; Curran, Kaitlin M.; Yoshimoto, Janna A.; Avery, Anne C.; Avery, Paul R.
• Is Part Of: Journal of veterinary internal medicine. Volume 34:Number 1(2020)
• Page Start: 105
• Page End: 116
• Publication Date: 2019-11-06
• Subjects: clonality -- feline -- flow cytometry -- leukemia -- polymerase chain reaction for antigen receptor rearrangements; Veterinary medicine -- Periodicals; 636.0896
• DOI: 10.1111/jvim.15650
• Languages: English
• ISSNs: 0891-6640

Abstract

Abstract: Background: Lymphocytosis is relatively common in cats, but few studies describe lymphocyte populations or the clinical course associated with different immunophenotypic expansions. Hypothesis/Objectives: We hypothesized that cats frequently develop non‐neoplastic lymphocytosis and that different neoplastic immunophenotypes have variable prognoses. We aimed to characterize the lymphocyte expansions in a large population of cats with lymphocytosis and to assess clinical presentation and outcome in a subset. Animals: Three cohorts of cats older than 1 year with lymphocytosis (>6000/μL) were examined to define immunophenotypic categories (n = 146), evaluate outcome (n = 94), and determine prevalence of immunophenotypes (n = 350). Methods: Retrospective study of cats with blood submitted for flow cytometry. Medical records (n = 94) were reviewed for clinical data, treatment, and survival information. Results: Five major immunophenotypic categories were identified: B cell, heterogeneous (≥2 lineages expanded), CD4+ T cell, CD4−CD8− (double negative [DN]) T cell, and CD5‐low‐expressing T cell. B‐cell and heterogeneous phenotypes were more consistent with a non‐neoplastic process, having polyclonal antigen receptor gene rearrangements, younger age at presentation, lower lymphocyte counts, and prolonged survival. The neoplastic phenotypes, CD4+ T cell, DN T cell, and CD5 low T cell, had different median survival times (752 days [n = 37], 271 days [n = 7], 27.5 days [n = 12], respectively). Among CD4+ T‐cell cases, cats with abdominal lymphadenopathy, intestinal involvement, or both and females had shorter survival. Among 350 cats with lymphocytosis, CD4+ T‐cell lymphocytosis was most common, followed by heterogeneous and B‐cell phenotypes. Conclusions and Clinical Importance: Neoplastic CD4+ T‐cell lymphocytosis is common in cats and has a prolonged clinical course compared to aberrant T‐cell phenotypes. Cats with heterogeneous and B‐cell lymphocyte expansions commonly have non‐neoplastic disease.