Development of Thyroid Carcinoma During Treatment With Pembrolizumab in a Lung Cancer Patient

Pembrolizumab, a programmed death 1 inhibitor, has been shown to have clinically significant efficacy in different types of cancer, providing long-term survival benefit for patients with lung cancer. Herein, we report the development of a primary thyroid cancer in a lung cancer patient that was being treated with pembrolizumab. Primary thyroid malignancy (and not only metastatic disease or immunotherapy-induced thyroiditis) should be considered in patients with lung cancer being treated with immune checkpoint inhibitors who develop new incidental thyroid lesions on imaging studies.