Thyroid ectopia of the liver: An unusual diagnosis with contrast-enhanced EUS (with video).

Asymptomatic 61-year-old woman with a surgical history of total thyroidectomy due to symptomatic colloid goiter 19 years prior was referred to our institute for an incidental hepatic mass. Abdominal computed tomography (CT) revealed an 8 cm × 5.5 cm × 6 cm lesion of the porta hepatis with irregular margins and focal calcifications, adjacent to the gallbladder and the pancreatic head. The lesion showed heterogeneous enhancement following contrast medium administration [Figure 1a]. The patient was then scheduled for EUS examination for further characterization of the lesion. EUS showed a 6 cm inhomogeneous solid cystic lesion with irregular margins and some tiny calcifications, localized in hepatic segment V and adjacent to the gallbladder [Figure 1b]. Following intravenous injection of ultrasonographic contrast agent (Sonovue, Bracco), the lesion showed prolonged, inhomogeneous, and diffuse contrast enhancement [Video 1]. We then performed EUS-guided fine-needle biopsy (FNB) with a 20G fenestrated needle (EchoTip ProCore, Cook Medical) from the duodenal bulb. Cytohistological examination revealed several fragments of thyroid tissue comprised mixed follicles with bland-appearing follicular cells and colloid [Figure 2a]. Immunohistochemistry showed positive staining for CK7, CK19, PAX8, and thyroid transcription factor 1 [Figure 2b], with negative staining for Hep Par1 and synaptophysin. Ki67 highlighted a low (<1%) proliferation index. These findings were consistent with ectopic thyroid tissue. The histologic diagnosis was confirmed by a I123-scintigraphy, showing active thyroid tissue in the liver, with no other active sites. Subsequent whole-body positron emission tomography-CT, showed no radionuclide pathologic uptake. Based on a multidisciplinary decision, a strict follow-up was planned, and no progression of the lesion was detected after 6 months. The estimated prevalence of thyroid ectopia is 1/100,000–300,000,[1] with lingual thyroid accounting for approximately 90% of cases.[2] Intra-abdominal ectopic thyroid tissue is exceptionally rare, and few cases in the liver have been reported.[3] This is the first documented case of thyroid ectopia within the liver diagnosed with contrast-enhanced EUS and FNB.

Figure 1

Contrast-enhanced computed tomography scan showing an irregular solid-cystic lesion with irregular margins and inhomogeneous contrast enhancement (circled) in segment V of the liver. Tiny calcifications are visible within the lesion (arrows) (a). B-mode EUS view showing irregular solid cystic lesion adjacent to the gallbladder (*) (b)

Figure 2

Ematoxilin-eosin view: Fragment of thyroid tissue comprised of mixed follicles (*) with bland-appearing follicular cells and colloid inside (a). Immunohistochemistry showing positive staining for thyroid transcription factor-1 of follicular cells (b)

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