PET scan evaluation of thymic mass after autologous peripheral blood stem-cell transplantation in an adult with non-Hodgkin's lymphoma.

We report the case of a 31-year-old man with anaplastic large-cell lymphoma successfully treated with chemotherapy who showed mediastinal widening 5 months after autologous stem-cell transplantation. CT scan and PET evaluations were consistent with the diagnosis of benign thymic hyperplasia. Because of the rapid and aggressive course of this type of lymphoma, and the progressive widening of the mass at CT scan, we performed a mediastinal biopsy that confirmed these findings, showing normal thymic tissue. This is the first case of benign thymic hyperplasia defined with FDG-PET and confirmed by histologic evaluation.