Isolated Pulmonary Cryptococcosis Confused with Lung Tumor 5 Years After Kidney Transplantation: A Case Report.

ABSTRACT

BACKGROUND: In transplant recipients, due to the use of immunosuppressive therapy, it is occasionally difficult to distinguish between an infection and malignancy, especially in the case of a lung lesion. Here, we report a case of isolated pulmonary cryptococcosis after kidney transplantation that was difficult to distinguish from a lung tumor. CASE REPORT A 52-year-old man underwent a kidney transplant from his mother when he was 44 years old. Immunosuppression was maintained with tacrolimus, methylprednisolone, and mycophenolate mofetil. His post-transplant course was uneventful and serum creatinine levels were maintained. Five years post-transplantation, a non-contrast computed tomography (CT) examination revealed a nodule measuring 3 mm in diameter in the middle lobe of the right lung. The nodule gradually increased to 12 mm in 2 years. Positron emission tomography/CT examination showed a maximum standardized uptake value of 0.5 for the nodule. Biochemical examination revealed no elevation in total leucocyte count and C-reactive protein levels. However, tumor markers were elevated serum carcinoembryonic antigen, 5.9 ng/mL; pro-gastrin-releasing peptide, 84.6 pg/mL. Furthermore, the serum cryptococcus antigen was negative. Therefore, thoracoscopic partial lung resection was performed. Pathologically, a number of spherical fungi from the necrotic substance of the tumor were confirmed positive by periodic acid-Schiff and Grocott-Gomori staining. The patient was therefore diagnosed with pulmonary cryptococcosis. Two years later, the patient is alive and has shown no evidence of recurrence. CONCLUSIONS: In lung nodules after kidney transplantation, even if serum cryptococcus antigen is not identified, it is necessary to keep in mind the possibility of pulmonary cryptococcosis.