A 59-year-old woman with a history of both breast and lung cancer developed a new 1.5 cm solitary pulmonary nodule on computed tomography (CT) scan. The nodule had increased 18F-fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET) with a standard uptake value (SUV) of 3.4. A CT guided biopsy was performed, and Mycobacterium avium complex (MAC) was identified. PET scans have become an important part of the diagnosis, staging, and follow-up of cancer. Even in individuals at considerable risk for cancer with a solitary nodule demonstrating increased FDG uptake, further diagnostic evaluation and needle biopsy might receive consideration prior to surgical intervention.