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The purpose of this study was to determine the immunophenotype and histologic classification of 50 cases of feline gastrointestinal lymphoma. Classification was determined using the National Cancer Institute Working Formulation and the Revised European and American Lymphoma/World Health Organization classification system. Tissue sections were stained with HE, phosphotungstic acid hematoxylin, anti-CD3, anti-CD79a, and anti-BLA.36. Overall, B-cell tumors predominated at 54% (27/50), including 16 diffuse large with immunoblastic nuclear type, 2 diffuse large with centroblastic nuclear type, 3 small lymphocytic, 4 lymphocytic intermediate type, and 2 T-cell-rich large B-cell lymphomas. T-cell tumors comprised 38% (19/50), including 15 epitheliotropic small lymphocytic and 4 lymphoblastic. Three tumors (6%) were nonreactive for B- and T-cell markers and had eosinophilic cytoplasmic granules when stained with HE. Gastric tumors were diagnosed in 24% (12/50) of cats, and 18% (9/50) were present only in the stomach. All gastric lymphomas were of B-cell lineage. Small intestinal lymphoma predominated, with 74% (37/50) of cats affected: T-cell tumors comprised 52% (19/37); 38% (14/37) were B-cell tumors; 8% (3/37) were nonreactive for B- and T-cell markers; and 2% (1/37) expressed both CD3 and BLA.36. Of the 8 cats (16%) that had lymphoma of the large intestine, 88% (7/8) had B-cell tumors and 12% (1/8) had T-cell tumors. The strongest association between gastrointestinal lymphoma immunophenotype, histologic classification, and location occurred in the stomach, where there was a predominance of diffuse large B-cell lymphoma of immunoblastic nuclear type.

Platelets contribute to prethrombotic or thrombotic states; however, accepted evaluation methods (i.e., in vitro testing by use of an aggregometer) of platelet function in cats can be difficult because of the large volume of blood required from which platelets are isolated and the potential for platelet activation due to difficult venipunctures in sometimes uncooperative or excited animals. The activation problem also contributes to errors in platelet counts. Platelets from four domestic short haired cats (two males, two females, 2-3 years old) minimally restrained without sedation or anesthesia were evaluated. Blood (5 ml) was collected by jugular venipuncture directly into syringes containing 3.8% trisodium citrate (nine parts blood to one part anticoagulant) plus prostaglandin E1 (3 microM; 0.25, 0.5, 1, or 2 microliters/500 microliters citrate) or 3.8% trisodium citrate alone. Prostaglandin E1, which is a stable metabolite of arachidonic acid with platelet inhibitory properties similar to those of prostaglandin I2, was added to the anticoagulant to prevent activation of platelets during the collection process. Feline platelets exposed to prostaglandin E1 became immediately and persistently nonreactive to agonists, which negated their use in functional studies (aggregation, 14C-serotonin release, binding of fluorescein-conjugated antifibrinogen) but improved platelet counting accuracy. Detection of in vivo activation of platelets in prethrombotic and thrombotic states in humans has been done by identification of activation-dependent molecules on platelet surfaces by use of specific antibody recognition and detection by flow cytometric analysis. Many activation-dependent platelet surface receptor changes are species specific; however, fibrinogen appears to be conserved across species.(ABSTRACT TRUNCATED AT 250 WORDS)