1. Introduction
Parathyroid glands normally descend from their embryologic origin in the pharyngeal pouches to their final locations in the central neck. However, aberrant migrations can lead to one or more parathyroid glands being in non-anatomic locations, including retroesophageal space, thymus, mediastinum, or within the thyroid gland. Rarely they fail to migrate, resulting in an undescended gland. Adenomas arising from these locations should be considered when initial preoperative imaging fails to identify a target adenoma or after unsuccessful surgery. Here we present a case of an ectopic parathyroid adenoma arising at the level of the pyriform sinus.