Positron emission tomography: useful in detecting metastatic cancer of unknown primary site

Metastatic cancer of unknown primary site represents approximately three percent of all new cancer diagnoses. Expensive and invasive diagnostic procedures are often performed although the primary tumour is detected in less than 25 percent of cases. We present a 63-year-old woman presenting with low back pain and was found on positron emission tomography (PET) to have lung cancer. The pros and cons of PET in the diagnostic process of patients with metastatic cancer of unknown primary site are reviewed. PET should be considered in the diagnostic process of patients with unknown primaries, and unnecessary invasive procedures may be avoided.