Complex sentence: Avian Sarcoma Leukosis Virus is characterized by a wide range of tumors, the most common are lymphomas and an enlarged liver due to infiltration of cancerous lymphoid cells.
Split into simpler sentences: Avian Sarcoma Leukosis Virus is characterized by a wide range of tumors, the most common of which are lymphomas. The disease is also characterized by an enlarged liver due to infiltration of cancerous lymphoid cells.