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

: Cancer spontaneous regression is a known manifestation rarely described for thoracic malignancies. We present the case of a patient affected by an EGFR-mutant adenocarcinoma who developed a contralateral aspiration pneumonitis months before surgery and manifested a complete pathological regression without any preoperative oncological 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. Tumor microenvironment appears to be not an "inert spectator", but an "active protagonist" on the course of the disease as well as on its therapeutic targeting.