Ectopic thyroid tissue accompanied by distinct blood supply and lymphoid tissue within the carotid sheath - a case report.

RATIONALE: Ectopic thyroid tissue (ETT) is not extremely rare, but it may be overlooked in clinical practice because of its frequently asymptomatic presentation, lack of urgency for diagnosis, and limitations in diagnostic techniques. We report a case of ETT within the carotid sheath and emphasize its distinct blood supply and accompanying lymphoid tissue, which may improve our understanding of the relationship among the ETT, associated blood supply, and lymphoid tissue from an embryological perspective.

PATIENT CONCERNS: A 42-year-old male was found to have an asymptomatic mass on the right side of his neck during a routine physical examination.

DIAGNOSES: Color Doppler ultrasound demonstrated a thyroid gland in the normal location. The mass measured 1.3 cm × 0.9 cm × 0.5 cm in dimensions with well-defined margins, had a similar echotexture to that of the thyroid gland, and a very short venous trunk draining directly into the internal jugular vein.

INTERVENTIONS: The patient underwent surgical excision of the mass. Histopathological examination after excision confirmed ETT with eminent vasculature and adjacent lymphoid tissue.

OUTCOMES: The postoperative course was uneventful. The patient has been followed up for 5 years, during which neither recurrence nor thyroid dysfunction was observed.

LESSONS: ETT can occur within the carotid sheath even in the presence of a normally located thyroid gland. A distinct vascular supply may represent a useful imaging clue for its diagnosis. Further studies are warranted to investigate the potential embryological association among ETT, its vasculature, and adjacent lymphoid tissue during thyroid descent.