ABSTRACT
All of the cell types that comprise the immune and haemopoietic systems and their developmental stages have the potential for malignant transformation (619). The aetiology of any tumour is multifactorial and there is progression through initiation and latent phases to clinical disease (620). Factors involved in the development of haemopoietic and immune system tumours in the dog and cat are poorly understood, with the single exception of tumours induced by FeLV. Predisposing factors in oncogenesis include genetic background, age, sex, diet, environment, immune suppression and stress. There are likely to be
619 Tumours of the immune system. This diagram depicts the developmental stages of lymphoid and haemopoietic cells and lists the major tumours that may arise from each cell type. Cells at different stages of development may become neoplastic and this may be reflected in the anatomical location of the tumour, its histological and cytological appearance, and the range of surface membrane molecules displayed by the transformed cells.
