CYTOHISTOLOGICAL AND IMMUNOLOGICAL CLASSIFICATION OF CANINE MALIGNANT-LYMPHOMAS - COMPARISON WITH HUMAN NON-HODGKINS-LYMPHOMAS

Non-Hodgkin's lymphomas (NHLs) in man are on the increase. They are al so common in dogs, which, as close companions of man, may constitute a useful experimental model. However, comparisons cannot be made withou t a reliable morpholopical and immunological classification of canine NHL. Canine nTHLs (n=134) were classified on the basis of fine-needle lymphnode aspirates according to the Kiel classification, and 92 were re-classified according to the Working Formulation and the updated Kie l classification, in a histological and immunological study. The immun ophenotype was determined (1) in 92 cases by the use of the pan-T anti -CD3 polyclonal antibody and the pan-B anti-mbl monoclonal antibody on paraffin wax-embedded tissue sections; and (2) in 47 cases by the use of a panel of polyclonal and monoclonal antibodies on fresh preparati ons and frozen tissue. Cytological analysis showed a predominance of h igh-grade lymphomas (73.9%) over low-grade lymphomas (26.1%); it also demonstrated forms not reported in other species (small-cell variants, lymphomas with macronucleolated medium-sized cells [MMCs], and polymo rphic lymphomas with a centroblastic component). Histological examinat ion revealed the rarity of follicular lymphomas (2.2% of cases), an ap pearance suggestive of T-cell neoplasia (8.7% of cases), and evidence that some MMC lymphomas originated in the marginal perifollicular zone s. Some (26%) of the lymphomas were of the T-cell phenotype: the major ity of these consisted of small-cell, low-grade lymphomas and mycosis fungoides, the rest being either high-grade pleomorphic lymphomas (mix ed or large-cell) or, rarely, high-grade, small noncleaved-cell, plasm acytoid lymphomas. No lymphoma expressed a double (T and B) phenotype. This study revealed similarities with, but also notable differences f rom, human NHL. Ill particular, the MMC lymphomas may constitute an in teresting equivalent or human marginal zone B-cell lymphomas. (C) 1997 W.B. Saunders Company Limited.