Spontaneous regression of squamous cell carcinoma of the lung with high PD-L1 expression: A case report and literature review

Abstract

Introduction: Lung cancer is the leading cause of cancer-related mortality worldwide. Squamous cell carcinomas (SCC) are responsible for a significant proportion of this burden. Spontaneous remission of cancer is a known phenomenon, albeit a rare event. The exact etiological mechanism(s) are not appreciated, although are largely predicated on the complex interactions between the malignant cells, tumor microenvironment and the immune system. Case Report: We present the case of an incidentally found, biopsy proven lung SCC with high PD-L1 expression that underwent spontaneous regression (SR) prior to definitive therapy. The patient underwent computed tomography (CT)-guided biopsy of the lesion and coronary artery bypass grafting in the time preceding the tumor regression. The observed regression has been sustained during ongoing follow-up. Conclusion: There are complex interactions between malignant cells, the tumor microenvironment, and the immune system, with evasion of immune destruction being a well-recognized and studied hallmark of cancer. There are multiple factors that may contribute to immune recognition of cancer and its subsequent regression and cases such as this highlight that there is much yet to elucidate. Further identification of these cases and their molecular characteristics will add to our understanding of the process. In the unknown lies the promise of improving cancer outcomes.