Monoclonal antibodies that inhibit the interaction between PD1 and PD-L1 are approved for clinical use in several cancer types, and they are also in clinical trials for additional indications, including thyroid carcinomas. A few papers have reported on PD-L1 expression in thyroid carcinomas, including a recent large study by Ahn et al. in Endocrine-Related Cancer using tissue microarrays on differentiated and anaplastic thyroid carcinoma. However, the expression of PD-L1 in medullary thyroid carcinoma (MTC) has not been reported so far, even though ongoing clinical studies aim to test the effectiveness of checkpoint inhibitors in this rare histotype as well. We thus assessed PD-L1 expression in both tumor cells and tumor-infiltrating immune cells in a series of 16 MTC cases at a tertiary center. Tumor cells were positive in only one case, which had 5% positive cells. 1% and 2% of the inflammatory cells were stained in two cases. No correlation was evident between PD-L1 expression and survival in our series. Our results are indicative of near uniform absence of PD-L1 expression in MTC and its accompanying inflammatory cells; these results should be replicated on a larger scale in other centers. Definitive answers regarding the utility of PD1/PD-L1 immunophenotyping in MTC and of the use of checkpoint inhibitors in the treatment of this aggressive and rare thyroid cancer are expected from ongoing clinical trials, which should perform correlations with PD1/PD-L1 expression.