Adenomatous hyperplasia arising from dual ectopic thyroid

Abstract

Ectopic thyroid tissue is an uncommon embryologic aberration characterized by the presence of thyroid tissue in a site other than its usual pre-tracheal location. Single ectopic thyroid tissue is the most common variant, and the base of the tongue is the most frequent ectopic location. Dual ectopic thyroid is extremely rare, and only eleven cases have been reported in the English literature. Furthermore, adenomatous hyperplasia has never been reported to arise from dual ectopic thyroid. There has been only one reported case of adenomatous hyperplasia arising from a single intratracheal ectopic thyroid. We report a case of adenomatous hyperplasia arising from dual ectopic thyroid tissue that presented as a sublingual mass in a 37-yr-old woman. The diagnosis was made through pathologic examination after surgical resection. We also discuss the diagnosis and treatment of ectopic thyroid, along with a review of the literature.

Keywords: Adenomatous hyperplasia; Dual ectopic thyroid; Lingual thyroid.

Fig. 1

Telescopic image: it shows 2×2 cm sized mass protruding in base of tongue (arrow).

Fig. 2

Contrast-enhanced neck MDCT axial view: (A) It shows a well-delineated, 2×2 cm sized well enhancing homogenous round mass in base of tongue (arrow). (B) Lower section of contrast-enhanced neck MDCT axial view shows 3×3 cm sized heterogenous moderate enhancing round mass in sublingual space (arrow). (C) Absence of thyroid gland in pretracheal region is detected.

Fig. 3

Tc-99m sodium pertechnetate thyroid scan: (A) It showed absence of normal thyroid gland in pretracheal area (arrowheads). (B) There were abnormal ectopic uptakes in submental area (arrow). Uptakes were overlapped making a fine distinction difficult.

Fig. 4

(A) An intraoperative photograph: Through a midline incision of mouth floor, we could see the reddish round mass (arrowheads). (B) Surgical specimen: it was a 3×3 cm sized firm, lobulated reddish mass covered with normal mucosa.

Fig. 5

Histopathologic findings: (A) Specimen was strongly positive for TTF (thyroid transcription factor) stain which proves that it is from thyroid tissue (TTF-1 stain, ×100). (B) It showed large follicular cells of thyroid tissue distended with colloid material which confirms the characteristic of adenomatous hyperplasia (arrow). There was no cystic change (H and E stain, ×100).