Features of large cell transformation of indolent lymphomas as observed on sequential PET/CT

Objective Detection of large cell transformation (LCT) has been reported with the increasing use of PET/computed tomography (CT) in patients with indolent lymphomas. However, there is little information on PET/CT characteristics, specifically, the distribution of lesion maximum standardized uptake value (SUVmax) within a patient, or SUVmax changes before and after LCT. Our objectives were to compare SUVmax values and distribution between nontransforrned and LCT patients; to compare SUVmax of LCT and nontransformed lesions in patients with documented focal transformation; and to measure the SUVmax changes in patients before and after LCT. Methods Retrospective study of patients with LCT (n=29) compared with nontransformed (n=41), and comparison of LCT and nontransformed lesions within patients and over time. Results On average, the highest SUVmax was greater in LCT patients than in nontransformed patients. In addition, there was a wider range of SUVmax values in the LCT group compared with the nontransformed group (P<0.05). The median ratio of the SUVmax of 12 LCT to nontransformed biopsy-proven lesions in the same patient was 4.3, P value of less than 0.05 (range 2.6-15.5). In 10 of 12 patients it was greater than or equal to 3. No change in highest SUVmax and distribution was shown on serial PET in untreated nontransformed patients. Conclusion LCT is often focal and is associated with higher SUVmax than nontransformed. The emergence of a focus with SUVmax three times or higher than others on a single scan, or that has tripled or more in value on serial scans, should raise suspicion for LCT. Nucl Med Commun 32:177-185 (C) 2011 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.