RESUMO
INTRODUCTION AND IMPORTANCE: The majority of surgical thyroid disorders are treated by thyroidectomy (total or hemithyroidectomy). Anatomical variants of embryologic origin may threaten the effectiveness of thyroid surgery and complete removal of thyroid tissue. CASE PRESENTATION: A female patient who underwent a total thyroidectomy, postoperatively had normal serum thyroid-stimulating hormone (TSH) levels without hormone replacement. Serum TSH and thyroglobulin levels were within normal range. A thyroid nuclear scan and chest magnetic resonance imaging (MRI) indicated a large retrosternal thyroid remnant. Clinical discussion: Separated thyroid remnant in the thyrothymic tract, forgotten during primary surgery, was the source of hormone production. Total thyroidectomy was not achieved due to embryologic remnant, and complete resection of thyroid tissue was affected by separated retrosternal thyrothymic rest. CONCLUSION: Surgeon awareness of anatomic variants of embryological origin undoubtedly improves thyroid surgery outcomes. Beside the anatomically based approach, total thyroidectomy could be achieved by an embryologically based approach.