Lymphocytic infiltration of the lungs is in most cases a bad thing. Lymphocyte infiltration in the lungs does not occur under normal circumstances, but only when the organism is damaged or attacked. Lymphocyte infiltration in the lungs can be caused by a number of factors, such as inflammation of the lungs, which can cause lymphocyte infiltration and produce an inflammatory response to fight the invasion of pathogens. Lung trauma can also cause lymphocyte infiltration, which is a normal defense mechanism of the body. Lung tumors can also cause lymphocytic infiltration, most often manifesting as invasion of the surrounding lymphoid tissue, which is generally indicative of tumor progression. Lymphocytic infiltration in the lungs should be treated promptly and according to the doctor’s instructions to avoid delaying the condition.