A frequent clinical dilemma in lung cancer care is the management of multifocal lung cancers. The management decision is based on determining if multiple cancers represent true independent primary cancers or related metastasis. This determination is critical to the appropriate staging of the cancers and treatment. Indeed, this distinction represents the difference between aggressive local therapy with either surgery or radiation therapy for primary early stage lesions, or palliative chemotherapy or best supportive care with appropriate symptom management for advanced stage metastatic disease.