A case of pulmonary cryptococcosis diagnosed by excisional biopsy in a renal transplant recipient

A 52-year-old man who had undergone a living renal transplantation had been receiving immunosuppressive therapy with methylprednisolone, tacrolimus, and mycophenolate mofetil for 6 years and had remained free from rejection. A pulmonary nodule with a diameter of 12 mm was detected in the right middle lobe of the lung. Because of the risk of malignancy, the patient underwent surgery for the diagnosis and treatment of the nodule. The nodule was resected under video-assisted thoracoscopic surgery and an intraoperative rapid diagnosis confirmed an inflammatory nodule. A subsequent pathological examination revealed a round, yeast-like fungus detected using periodic acid-Schiff staining and Grocott staining, supporting a diagnosis of pulmonary cryptococcosis. A blood sample tested negative for cryptococcal antigen, so additional treatment was not prescribed. While transplant recipients require immunosuppressive therapy after transplantation, such treatment increases the incidence of infection and malignant disease. A pathological examination after an excisional biopsy should be used to diagnose pulmonary nodules developing in patients receiving immunosuppressive therapy.