Objective: The aim of this study is to define primary focus detection efficiency of PET/CT in patients with carcinoma of unknown primary.

Material and Method: Fifty one patients- who diagnosed with carcinoma of unknown primary detected with PET/CT to define the primary focus- were included in this study. Increased F-18 FDG foci were evaluated by visual and semiquantitative analysis.

Results: Fasting blood glucose levels were between 82 and 149 mg/dl(average 105.14). SUVmax values calculated from 0 to 17.50 (average8.126). In 23 patients (%45.1) adenocarcinoma, 16 patients (%31.4) carcinoma, 4 patients (%7.8) malignant epitelial tumor, 3 patients (%5.9) non small cell carcinoma, 2 patients (%3.9),squamous cell carcinoma, 1 patient (%2) small cell carcinoma,1 patient spindle cell carcinoma and 1 patient renal cell carcinoma were detected histopathologically. In 13 patients (%25.5) there was no evidence of primary focus, 15 patients (%29.4) lung, 8 patients (%15.7) colon, 5 patients (%9.8) pancreas, 3 patients (%5.9) liver, 2 patients (%3.9) stomach, 1 patient (%2) pleura, 1 patient (%2) uterus, 1 patient (%2) kidney, 1 patient (%2) nasopharnyx and 1 patient (%2) primary peritoneal lesion has detected as primary according to PET/CT results.

Conclusion: As a result, PET/CT has been identified the primary focus in 38/51 (%72.5) patients. We think PET/CT has a promising future in patients with carcinoma of unknown primary to determine the primary focus.