The avian leucosis virus induces lymphoma in chicken called lymphoid leucosis. This disease causes severe loss due to mortality of poultry birds and depressed performance. The avian leucosis virus (ALV’s) are prevalent throughout the world. The present paper describes histopathology of liver with lymphoid leucosis. Four commercial egg type white dead birds, thirty three weeks old with no previous sign of ill health were received from a commercial layer poultry farm of Karachi. On post mortem the liver was enlarged. A portion of liver was preserved in 10% formalin and processed for histological studies. Dehydration was carried out in serial concentration of known volume of ethanol. Dehydrated tissue was then imbedded in paraffin wax at 52°C for 12 days. During the wax infiltration process air bubbles were removed from the tissue. Using rotary microtome 10 µm thick sections were cut and stained with haemotoxylin and eosin. Photomicrographs were taken using an automatic photographic camera mounted on a microscope Nikon Optiphot-2. The sections of liver show heavy infiltration of lymphoid cells. The infiltration of cells in the liver was marked where there was loss of hepatocytes. Lymphoid cells at high magnification revealed that the cells consisted of small and large lymphocytes with scanty and ample cytoplasm. The scanty cytoplasm of large lymphocytes appears poorly stained while the small lymphocytes present are deeply stained. There is no definitive treatment for lymphoid leucosis available.
