Thanks for your question on HCM. Diffuse large B cell lymphoma is blood malignancy. In blood malignancy immunity of the patient is very compromised. And chemotherapy makes it even worse. So these patients are at great risk of infection. In such patients infections tend to stay longer and chances of resistant or uncommon infection are more. So possibility of Fungal infection, tubercular infection or parasitic infection is high. Since you are having chronic lung infection , fungal and tubercular infection appears more . Better to consult pulmonologist and get done bronchoscopy and BAL (Bronchoalveolar lavage) analysis to find out the causative organism and start appropriate treatment.