RESUMEN
The thyroid gland is an endocrine organ comprising two lobes connected by an isthmus. Thyroid isthmus agenesia (TIA) is a rare anatomical anomaly, which has only been documented in a limited number of case reports. This report presents the case of a 49-year-old female patient who was diagnosed with intraoperative TIA during diagnostic thyroid lobectomy. The patient was arranged for a diagnostic lobectomy of the right thyroid lobe after identifying an atypical nodule of undetermined significance, in the right lobe, which had been confirmed with two distinct biopsies. The patient was discovered to have isthmus agenesia during a neck exploration performed under general anesthesia. Owing to its rarity, the precise clinical and anatomical characteristics of TIA have not been defined, and its underlying cause is still not completely understood. The detection of TIA warrants the considerations of any other accompanying diseases. Prior identification and assessment of surgical approach are crucial for ensuring a secure surgical procedure and mitigating the risk of surgical complications. Nevertheless, caution must be exercised if TIA is detected during operation because preoperative identification is not always feasible. In summation, additional patient reports and studies are required to uncover the underlying cause of this pathological condition.