Prevalence of synchronous second primary malignancy: identification using whole body PET/CT imaging

Objective To describe the prevalence of synchronous second primary malignancy detected by PET/ CT in our clinical practice and its differentiating features from metastatic lesion. Methods All PET/CT scans from 1st October 2009 to 30th September 2010 were reviewed. The suspected cases of synchronous second primary malignancy detected by PET/CT were selected, and the histologically confirmed ones were being illustrated. Metachronous second primary cases were excluded. Results A total of 1522 scans were reviewed. sixty-eight cases were suspected to have a synchronous second primary while 8 were histologically confirmed. Seven (0.4%) of them were malignant and 1 was a benign tumor. These 7 cases were illustrated, and we found a significant difference in SUVmax values and site of occurrence unusual to metastasis that were the two main radiological features differentiating them from metastatic lesion. Conclusion Synchronous second primary malignancy could be missed without the use of whole body imaging. Its diagnosis is of utmost importance to prevent erroneous upstaging of disease and subsequent palliative treatment instead of curative surgery.