Value of FDG-PET in ocular adnexal lymphoma (OAL) compared with MR imaging

Objectives To evaluate the imaging characteristics of FDG-PET and MR imaging of OAL patients.

Methods We evaluated 55 patients who had been examined by FDG-PET and MRI at diagnosis with biopsy-proven malignant lymphoma at 64 sites. All informations were obtained from a retrospective review of medical records, findings of FDG-PET, and MRI.

Results Fifty five patients (mean age 65 years) with gender distribution of 31 females and 24 males were included. The major histopathologic subtypes were mucosa-associated lymphoid tissue (MALT) in 39 patients and non-MALT in 16 patients (including one T-cell lymphoma); follicular lymphoma (n=5), diffuse large B-cell lymphoma (n=8) and other one each: mantle cell lymphoma, senile EBV-positive B-lymphoproliferative disorder, extranodal NK/T-cell lymphoma. Mean size of tumor is 1.94 cm (range 0.4-5.6). MRI of 63 sites showed 43 isointense, 11 hypointense and 9 hyperintense on T1-weighted imaging, 54 hyperintense, 9 isointense on T2-weighted imaging, and 49 moderate enhancement, 3 slight enhancement and one non-enhancement with gadolinium injection (n=53). FDG-PET upstaged 9 patients with systemic lymphoma involvement, having a higher sensitivity than MR imaging. The SUVmax of FDG was <1.5 at 5 sites (MALT: n=5), 1.5~2.5 at 26 sites (MALT: n=25, DLBCL: n=1) and >2.5 at 33 sites. Sensitivity in MALT (40.4%) was lower when compared with non-MALT (93.8%). Twenty six patients were followed up FDG-PET, which detected relapse in 6 of them. Other findings were: high LDH in 5 of the 55 patients, high serum interleukin 2 receptor in 30 of 54,CD5 positive in 6 of 55,and Bcl 6 positive in 14 of 45.

Conclusions MRI is essential in the evaluation (location, size, degree of infiltration) of OAL. We identified FDG avidity in 51.8% of OAL but in 40.4% of orbital MALT, in 93.8% of non-MALT. However, these results suggested that FDG-PET is a useful tool with which to stage, restage after therapy, or monitor disease in patients with OAL