Lymphocytic Thyroiditis Is a Cytopathologic Feature of Nivolumab-induced Thyroid Dysfunction.

Immune checkpoint inhibitors are widely used in the treatment of various cancers. These medications are associated with immune-related adverse events (IRAE) affecting multiple organ systems. Endocrine diseases are among the most common associated IRAEs and the thyroid is often involved. However, the pathologic features of IRAE are not well established. We find that lymphocytic thyroiditis is a cytopathologic feature of nivolumab-induced thyroid dysfunction and this finding sheds light on understanding the pathology and mechanism of thyroid IRAE.