Ultrastructure of swine myelogenous leukaemic cells, with particular reference to intracytoplasmic granules

Seven cases of swine myeloid leukaemias were investigated by light and electron microscopy. All animals were adult sows. Morphologically these cases were classified as myeloblastic leukaemia with maturation (Cases 1 to 6) and chronic myeloid leukaemia (Case 7). The neoplastic cells were composed of immature promyelocytoid cells in Case 1. In Cases 2, 3, 4 and 5 there were immature or mature promyelocytoid cells containing peroxidase-positive granules. In Case 6, the neoplastic cells consisted of promyelocytoid cells and myelocytoid cells. The latter predominated and contained not only peroxidase-positive granules but also peroxidase-negative ones. The neoplastic cells in Case 7 showed various stages of cell maturation. The morphological characteristics in our cases resembled those in human myeloid leukaemias.