Abstract
Anaplastic and poorly differentiated thyroid carcinomas are the two most aggressive forms of thyroid cancers and carry significant morbidity and mortality despite multimodal therapeutic approaches. Anaplastic thyroid carcinoma (ATC) and, to a lesser degree, poorly differentiated thyroid carcinoma (PDTC) have a high tumor mutation burden, and immunologically hot tumor microenvironment when compared to well-differentiated thyroid carcinomas. As such, immunotherapy, and in particular immune checkpoint inhibitors, have been hypothesized to be effective against these cancers. This review aims to explore the biological rationale for immunotherapy in dedifferentiated thyroid carcinomas and to summarize the current evidence underlying this treatment modality.