Complete spontaneous regression of non-small cell lung cancer followed by adrenal relapse

Spontaneous regression (SR) of cancer is a rare phenomenon. SR is recognized as complete or partial disappearance of the disease after inadequate or no treatment. Although reports of this phenomenon have been documented for several malignancies, it is rare in patients with lung cancer. In most documented cases, diagnoses of SR were made based on only the radiologic findings. We herein report a case of complete SR of non-small cell lung cancer (NSCLC) that was pathologically proven using a resected specimen. Moreover, despite the local complete SR, the patient subsequently experienced an adrenal metastasis after surgery. To the best of our knowledge, this is the first report of a patient with NSCLC in whom complete regression of the primary site was observed, but in whom a distant metastasis became apparent. Both phenomena were pathologically proven. Our report suggests that both SR and tumor progression can proceed simultaneously.