Diagnostic value and reproducibility of fine-needle aspiration cytology in canine malignant lymphoma

Cytological examination of biopsy samples obtained by fine-needle aspiration appears to be an accurate and reliable basis for the classification of canine non-Hodgkin's lymphoma (NHL). Intra- and inter-observer reproducibility of both the original and the updated Kiel classification were assessed blindly on two occasions by two experienced cytologists who examined biopsy specimens from 78 dogs with NHL. Analysis by kappa statistics showed moderate to good intra-observer reproducibility and poor to moderate inter-observer reproducibility for the original Kiel classification. In the updated Kiel classification both intra- and inter-observer reproducibilities were good, probably due in part to the additional information provided by the immunotyping. The consensus cytological classifications were compared with those based on histology, and the association constant (Cramér's V) was 0.65 for the original Kiel classification and 0.70 for the updated Kiel classification. The results suggest that the updated Kiel classification in particular is suited to cytological classification of canine NHL.