The fine structure of lymphosarcoma in cattle.

Nine cases of bovine lymphosarcoma were classified by light microscopy as lymphoid or reticulum according to the predominant cell type, or as lymphoreticular when there was a heterogeneous mixture of lymphoid and reticulum tumor cells. Typical ultrastructural features of these cells were as follows. Lymphoid tumor cells had smoothly contoured nuclear and cytoplasmic membranes and few cytoplasmic organelles. Reticulum tumor cells had large interchromatin spaces and irregular nuclear and cytoplasmic outlines. They often had multivesicular bodies, lysosomal vesicles, and much smooth-surfaced endoplasmic reticulum in the cytoplasm and were frequently surrounded by extracellular microfibrils and collagen libers. Nuclear inclusion-like masses of cytoplasm were common in both types of tumor cells. No structure was observed which could be recognized as virus.