After optimal therapy, residual masses are defined as a mass greater than 2 cm of CT scann, and are present in 15 to 20% of mediastinal lymphomas. We prospectively studied 50 pts with gallium scan (32 cases) and a MRI (41 cases) after the diagnosis of residual masses. There were 38 Hodgkin's disease and 12 non Hodgkin lymphomas; stage I and II: 29 pts; stage III and IV: 21 pts; 32 cases had bulky mediastinal involvement at diagnosis.
Results: A negative gallium scan and/or a fibrotic signal on MRI was correlated with a complete remission in 43/50 cases. We observed 2 false positive with gallium scan and 7 cases were MRI was not conclusive with a high signal of indeterminate tissue.
Conclusion: We propose to perform a gallium scan as soon as the residual mass is detected, than the follow up will be made an MRI. Surgical biopsy must be proposed only when both exams positive or not conclusive.