DETERMINAZIONE CITOFLUORIMETRICA DEL KI67 IN DIVERSI SOTTOTIPI CITOLOGICI DI LINFOMA CANINO (FLOW CYTOMETRIC DETERMINATION OF KI67 IN DIFFERENT CYTOLOGICAL SUBTYPES OF CANINE LYMPHOMA)

Quantification of Ki67 is useful in evaluating proliferative activity of neoplastic populations and tumor grading. In bibliography there are no works about flow cytometric determination of Ki67 in canine lymphoma (LSA) and there are no data concerning the evaluation of proliferative activity in cytological subtypes. Objective: Characterizing proliferative activity in different cytological subtypes of canine LSA by flow cytometry. Methods: 45 LSAs were classified according to update Kiel classification evaluating lymph node smears stained with MGG. Ki67 was determined on lymph node aspirates using a FITC-antibody (clone MIB1). Results: Cases were classified in 42 high grade (HG) and 3 low grade (LG) LSA. HG were: 27 centroblastic (CB); 6 pleomorphic (P); 4 immunoblastic (IB); 3 lymphoblastic (LB); 2 plasmocytoid (PC). LG were: 2 small clear and 1 pleomorphic small cell. Ki67 median values were significantly higher (P<0.05) in P (48%) and CB (39%) compared to LG (4%). Among HG, IB and PC showed lower median Ki67 values (18% and 21%, respectively) compared to P, CB and LB (41%) although difference did not reach statistical significance. Each HG cytological subtype presented a wide range of Ki67 positivity: CB= 10-85%; P= 24- 60%; LB= 27-58%; IB= 15-42%; PC= 13-29%. Discussion: In each cytological subtype of HG LSA a variable proliferative activity has been detected. This is an indicator of the heterogeneity characterizing canine LSA and this variability reflects the different entities with different biological behaviors that are part of canine LSA.