Clinical significance of axillary findings in patients with lymphoma during follow-up with 18F-fluorodeoxyglucose-PET.

PURPOSE: The aim of this study was to evaluate the clinical significance of positive axillary findings in patients with Hodgkin's disease and non-Hodgkin's lymphoma during follow-up with 18F-fluorodeoxyglucose-PET. MATERIALS AND METHODS: We retrospectively reviewed PET scans carried out in 543 patients during follow-up. Patients with reports describing any increased fluorodeoxyglucose uptake at the axillary level were selected (106 cases) and final assessment of the findings was available in 78 patients (17 Hodgkin's disease, 51 non-Hodgkin's lymphoma). PET scans were performed after standard procedure and reports were interpreted as positive or negative on the basis of visual analysis. At the moment of the scan all patients had no clinical or laboratory sign of relapse, and had not received therapy for at least 6 months. All PET results were compared with other diagnostic procedures (ultrasonography and computed tomography), biopsy and/or follow-up data. RESULTS: Of 78 patients, 24 were PET positive in one axilla, 23 had axillary findings and one or more other extra axillary sites, five patients were positive in both axillas and 26 were positive in both axillas and one or more other sites. Of the 24 patients with single axillary finding, the result for five was true positive and for 19 it was false positive. Sixteen cases of the 23 patients with PET positive at one axilla and other sites had a true positive result, whereas seven had a false positive result. Only one of five patients with both axillas being positive at PET turned out to be true positive; finally, 23 cases from the 26 patients with both axillas and other findings had a true positive result and three of 26 had a false positive result. Overall, 45 out of 78 patients were true positive and 33 were false positive. CONCLUSION: Axillary findings are relatively frequent and can be isolated or in association with other findings. In patients with axillary involvement only the frequency of false positivity results is elevated and therefore these cases need to be evaluated carefully. In contrast, axillary findings associated with other pathological localizations show true positive results in most cases, thus indicating a high likelihood of disease recurrence. Standardized uptake values showed a limited role for discriminating true-positive and false-positive findings.