Spontaneous Regression of an Epidermal Growth Factor Receptor-mutant Left Upper Lobe Adenocarcinoma

Spontaneous regression of cancer is a known mani-festation rarely described for thoracic malignancies. We present the case of a patient affected by an epidermal growth factor receptor-mutant adenocarci-noma who developed a contralateral aspiration pneu-monitis months before surgery and manifested a complete pathologic regression without any preopera-tive oncologic treatment. The underlying mechanisms are not clear, but immune system activation appears to be a key player, acting as a plausible trigger of a change in host response to cancer cells. The tumor microenvironment does not appear to be an "inert spectator" but rather an "active protagonist" on the course of the disease and its therapeutic targeting.(Ann Thorac Surg 2022;114:e261-e264) (c) 2022 by The Society of Thoracic Surgeons