Co-Occurrence of Hotspot Point Mutation and Novel Deletion Mutation of TERT Promoter in Solid Variant Papillary Thyroid Carcinoma in a Patient with Synchronous Esophageal Cancer

(1) Introduction: Telomerase reverse transcriptase (TERT) promoter mutations are associated with unfavorable clinical outcomes in papillary thyroid carcinomas (PTCs). Two substitution mutations, C228T (c.1-124C>T) and C250T (c.1-146C>T), make up most of the mutations and occur in a mutually exclusive manner. (2) Case presentation: A 72-year-old man was initially referred to a tertiary hospital for treatment of esophageal cancer. Preoperative imaging revealed a 3.2 cm thyroid nodule pathologically diagnosed as PTC on needle biopsy. The patient underwent thyroid lobectomy with esophagectomy and was finally diagnosed with synchronous solid variant PTC (SVPTC) and esophageal squamous cell carcinoma. Sanger sequencing using DNA from the thyroid tumor showed an indel mutation, c.1-132_1-124delinsT, composed of a deletion (c.1-132_1-125del) as well as a hotspot mutation (c.1-124C>T(C228T)) in the TERT promoter. (3) Conclusions: This is the first report of PTC harboring a novel deletion along with a hotspot mutation in the TERT promoter in a patient with synchronous esophageal squamous cell carcinoma.