Materials and Methods: 82 patients (45 women and 37 men) with a median age of 53.5 (21-88) years who had PET-CT for differential diagnose for MLAP were evaluated retrospectively. 31 (37.8%) patients diagnosed sarcoidosis, and 51 (62.2%) lymphoma that had histologically proven by various surgical procedures.

Results: There were no statistical difference between gender, age and average SUV max of groups (p = 0.068, p = 0.846, p = 0.338). 26 of 31 patient (83.9%) of sarcoidosis group had abnormal findings compared the lymphoma group (51.0%) which showed statistically significant difference (p = 0.003). Meanwhile there were no statistical difference between hilar lymph nodes and liver involvement among the groups (p = 0.239 and p = 0.917), cervical, axillary, abdominal lymph nodes and spleen involvement was significantly higher in the lymphoma group (p = 0.008, p < 0.001, p < 0.001 and p = 0.001). Bone marrow (BM) involvement were also significantly higher in lymphoma group (p < 0.001).

Conclusions: There are no specific MLAP findings to differentiate sarcoidosis from lymphomas by PET-CT. It is more likely that the pathological conclusion will be consistent with lymphoma rather than sarcoidosis, in case of involvement of cervical, abdominal and axillary lymph nodes, spleen and BM involvement; however abnormal pulmonary parenchymal findings are in the favor of the diagnosis of sarcoidosis. Keywords : mediastinal lymphadenopathy, sarcoidosis, lymphoma, PET-CT