Thoracic and abdominal manifestations of lymphoma occurring in the immunocompromised patient.

Organ transplant and AIDS patients are at a much higher risk for developing non-Hodgkin's lymphoma than is the general population. This increased risk is directly related to chronic immunosuppression and often is associated with viral infections. In contrast to lymphomas occurring in nonimmunocompromised patients, these tumors typically are of higher grade, are more aggressive, have a worse prognosis, and exhibit a higher frequency of extranodal disease. The most frequent organs involved are the head and neck, bowel, liver, and lungs. Thoracic manifestations of ARL and PTLD are similar, consisting of nodular, diffuse alveolar, and interstitial pulmonary disease, mild to moderate mediastinal adenopathy, and pleural effusions. Of these findings, pulmonary nodules are the most specific, although they can be difficult to differentiate from Kaposi's sarcoma and opportunistic infections. Abdominal findings are also similar for the two diseases, with the most common lesions appearing as low attenuation, hypoechoic masses in the solid abdominal organs; ulcerating nodular or diffusely infiltrating bowel lesions; and bulky retroperitoneal, mesenteric, or omental adenopathy. The identification of solid masses in the abdominal organs in AIDS and transplant patients is highly suspicious for ARL and PTLD. Due to the overlap of imaging characteristics of different pathologies, however, biopsy usually is necessary to confirm the diagnosis. Both ARL and PTLD respond to therapy; however, the prognosis for patients with ARL is uniformly poor, whereas the prognosis for treated PTLD is remarkably good. An awareness of the imaging characteristics of ARL and particularly PTLD can have significant impact on prognosis by allowing for timely diagnosis and therapy.