Ectopic Thyroid Tissue in the Adrenal Gland: A Report of Two Cases with Pathogenetic Implications

Abstract

Background: Ectopic thyroid tissue is usually found anywhere along the embryonic descent pathway of the medial thyroid anlage from the tongue to the trachea (Wö lfler area). However, ectopic thyroid tissue in the adrenal gland (ETTAG) is not easy to understand on the basis of thyroid embryology; because it is so rare, the possibility of metastasis should first be considered. Here, we describe two cases of ETTAG with pathogenetic implications and review the associated literature. Patient findings: Two cases of ETTAG presented as incidental cystic adrenal masses in adult females, one having a congenital hernia of Morgagni. The ETTAG was histologically indistinguishable from normal orthotopic thyroid tissue, and its follicular nature was confirmed by immunohistochemical positivity for thyroglobulin, thyroperoxidase, thyroid transcription factor-1 (TTF-1/Titf-1/Nkx2.1), cytokeratin AE1/AE3, cytokeratin 7, pendrin, human sodium iodide symporter, paired box gene 8, and forkhead box E1 (TTF-2), as well as positivity for the messenger RNA of the thyroglobulin gene by in situ hybridization analysis. No C cells (negativity for calcitonin, chromogranin, and synaptophysin) were present. Neither BRAF nor KRAS mutations were detected with real-time polymerase chain reaction analysis. Further work-up did not show evidence of thyroid malignancy. Summary: ETTAG is a rare finding, with only seven cases reported; women are much more frequently affected than men (8:1), and it usually presents in the fifth decade (mean age 54, range 38-67) as a cystic adrenal mass incidentally discovered on abdominal ultrasonography and/or in computed tomography images. ETTAG is composed of normal follicular cells without C cells. The expression of some transcription factors (TTF-1, paired box gene 8, and FOXE1) involved in development and/or migration of the medial thyroid anlage is preserved. Coexistence of a congenital hernia of Morgagni in one patient suggests an overdescent of medial thyroid anlagederived cells in its pathogenesis. Conclusion: Although ETTAG pathogenesis remains unknown, the lack of C cells together with the coexistence of a congenital defect of the anterior diaphragm (hernia of Morgagni) in one of our patients could suggest an overdescent of medial thyroid anlage-derived cells in the origin of this heterotopia.

Ectopic Thyroid Tissue in the Adrenal Gland

“…7 Importantly, ETT consists of follicular cells and parafollicular cells have not been identified at sites of ectopic thyroid parenchyma in our case as well as in other reports. 19,23 In conclusion, ETT in the adrenal gland is a rare but well-documented occurrence. It nearly always takes the form of a cystic lesion with features that are distinctive enough to be recognized both macroscopically and histologically.…”

“…The majority of patients have no endocrine abnormalities, but in 2 there was hyperaldosteronism due to a concurrent benign cortical adenoma in the same adrenal gland with the ETT. 22,23 The pathologic features of adrenal ETT are very similar, to the point that they almost represent a distinct entity. In all cases, but one, the lesions were macrosopic cysts of a fair size, ≥3 cm in 8 of the 10 cases (Table 1), containing colloid-like material.…”

Laparoscopic resection of retroperitoneal ectopic thyroid tissue

“…Therefore, the ectopic thyroid tissue may have arisen because of abnormal migration or the heterotopic differentiation of uncommitted endodermal cells, but it is not possible to arrive at a definite cause, especially as there have been no similar cases reported. Immunohistochemistry, in situ hybridization, or other molecular studies might provide clues to the histogenesis of ectopic thyroid tissue .…”

“…Ectopic thyroid tissue is commonly found in the head and neck along the thyroglossal duct; it does not differ microscopically from tissue observed in the thyroid gland. Ectopic thyroid tissue has also been detected in the lungs, gallbladder, small intestinal mesentery, pancreas, and adrenal gland . However, the development of ectopic thyroid tissue in the retroperitoneum below the diaphragm is extremely rare.…”

Da Vinci robot-assisted resection to treat abdominal ectopic thyroid: A case report and literature review

“…The thyroid gland tissue is composed of two cell types, the C cells and the thyroid follicular cells [28]. Romero-Rojas et al [2] showed that the lack of C cells in histology and immunohistochemical pro les is one of the important diagnostic criteria.…”