Making Sense of Lymphoma Diagnostics in Small Animal Patients

SUMMARY Thereisnosinglestand-aloneassayforthediagnosis,characterization,andstagingoflymphoma in small animal patients. In addition to cytology and histopathology, immu-nophenotyping by flow cytometry, PARR, and immunohistochemistry or immunocyto-chemistry all provide important diagnostic and prognostic information. However, foraccuratediagnosisandstagingthefindingsmustbeevaluatedinconcertwiththeclin-ical history, physical examination, and other ancillary data. ACKNOWLEDGMENTS Figs. 3Band4 were graciously provided by Dr Bill Vernau, University of Californiaat Davis. The following collaborators shared their protocols and provided inputregarding preferred samples, standards for interpretation, and important controlsfor flow cytometric and PARR assays performed in their laboratories: Anne Avery(FortCollins,Colorado);MaryJoBurkhard(Columbus,Ohio);StefanoComazzi(Milan, Fig. 6. Canine case study. (A) The cytology preparation from an FNA of an enlarged lymphnode consists of numerous very large lymphocytes, many cytoplasmic fragments (arrow-heads), occasional plasma cells (short arrow) and small lymphocytes (long arrow), and scat-tered red blood cells (Wright stain, original magnification 100). (B) On histopathology, thelymph node architecture was replaced by a diffuse infiltrate of large lymphocytes with a sin-gle prominent central nucleolus (arrow) (hematoxylin-eosin stain, original magnification 400). (C) Flow-cytometric evaluation of a lymph node aspirate showed a prominent pop-ulation of cells with high forward and side scatter, and a few other cells with light-scatterproperties of neutrophils, small lymphocytes, and red blood cells. Large gated cells lackedCD3 and TCRa/b expression (D) and contained a few CD4