Background:   Post-transplant lymphoproliferative disease (PTLD) comprises a spectrum of clinically relevant lymphatic diseases that occur in patients after transplantation. The PTLD-related mortality is high and the clinical picture and location of the lesions are very variable. For these reasons, the diagnosis of PTLD is difficult and new diagnostic tools are sought.
Case Report: A 31-year-old woman, 17 years after kidney transplantation, presented with recurrent upper respiratory tract infections, fever, and weakness and was diagnosed with pulmonary PTLD. Computed tomography appearance was not typical for lymphoma and demonstrated multiple bilateral pulmonary nodules and masses with a halo sign. Initial differential diagnosis included invasive pulmonary aspergillosis and acute Wegener granulomatosis. Since cultures from bronchoalveolar lavage and anti-neutrophil cytoplasmic antibodies were negative, videothoracoscopy with lung biopsy was performed. Pathology analysis revealed diffuse large T-cell lymphoma with histopathologic features of infiltrative growth along the lung interstitium, vessel invasion, and hemorrhagic necrosis possibly explaining the presence of a halo sign.
Conclusions: We suggest PTLD should always be suspected in a transplant recipient presenting with the CT halo sign. Moreover, the correlation of this radiological phenomenon with the patient’s clinical presentation and severe pathologic findings allows us to conclude that the thoracic halo sign in PTLD may reflect a worse prognosis.

Keywords: Wegener Granulomatosis, CT, halo sign, IPA, PTLD