The incidence of synchronous second primary cancer (SSPC) with DIfferentiated Thyroid Cancers (DTC) is a very rare entity. Very few case reports and case series were published in the literature. To enumerate the clinicopathological data of patients with DTC with SSPC. This is a single-center retrospective study. All the patients diagnosed with DTC and SSPC from January 2016 to July 2023 were included in the study. The demographic, clinicopathological data, and survival data were collected from the institute's database. Twelve patients were found to have DTC with SSPC. All the patients had papillary thyroid cancer. Ten patients had head and neck squamous cell carcinoma, one patient had malignant phyllodes tumor, and another patient had endometrioid adenocarcinoma as the SSPC. Six patients were diagnosed during preoperative evaluation, one patient was diagnosed 3 months after the oral malignancy diagnosis, and five patients were diagnosed with PTC in cervical nodes after neck dissection. Complete thyroid removal was done in six patients and hemithyroidectomy in two patients. The median follow-up was 25.55 months. The median overall survival was 40.97 months. Head and neck SCC is the most common SSPC with DTC. Since these are rare scenarios multi-disciplinary panel discussion can help in deciding management.
