Double pyramidal lobe detected at ultrasound: a case report with review of the literature.

The pyramidal lobe (PL) is a common anatomical variant of the thyroid gland, arising from the caudal end of the thyroglossal duct during embryological development. Although its prevalence is approximately 40% in the general population, the presence of a double pyramidal lobe (DPL) is extremely rare. We report a unique case of preoperative ultrasound diagnosis of DPL, subsequently confirmed intraoperatively and histologically. A 61-year-old male with a long-standing toxic multinodular goiter under methimazole treatment underwent thyroid ultrasound, which revealed a markedly enlarged gland (98 mL) with bilateral nodular disease and two distinct pyramidal lobes originating from the isthmus. Fine-needle aspiration cytology showed benign findings. Due to substernal extension and tracheal deviation, total thyroidectomy was performed. Both pyramidal lobes, preoperatively identified by ultrasound, were successfully excised. Histopathological examination confirmed benign multinodular goiter without malignancy and validated the presence of two separate PLs. To our knowledge, this is the first reported case of DPL diagnosed preoperatively by ultrasound and confirmed histologically. Preoperative recognition of PL, and particularly DPL, is clinically relevant. Residual pyramidal lobe tissue after total thyroidectomy may contribute to persistent or recurrent disease. In malignancy, it can impair thyroglobulin-based surveillance and reduce radioactive iodine efficacy by competing for uptake. Given the potential surgical implications, careful preoperative ultrasound assessment by experienced operators is essential. This case highlights the importance of thorough anatomical evaluation and close collaboration between endocrinologists and surgeons to ensure complete thyroidectomy and reduce the risk of persistent or recurrent disease.