SAT-611 Abdominal Goiter

Abstract

A 79 year old woman with hyperlipidemia, hypertension, congestive heart failure was referred for evaluation of ectopic thyroid tissue found on a liver biopsy. The patient originally presented with abdominal pain and was noted to have a liver mass measuring 5.7 x 3.2 x 5 cm on computed tomography (CT) that appeared contiguous with the medial segment of the left hepatic lobe. A subsequent ultrasound (US) showed the same 3.1 x 4.7 x 4.7 cm ovoid mass with a central focus of increased echogenicity and a well-circumscribed margin; a fine needle aspiration (FNA) of the hepatic lesion showed thyroid follicular cells and abundant colloid. Magnetic resonance imaging of the abdomen was done 6 months later, which showed a soft tissue abnormality in the porta hepatis extending centrally into the liver of decreased T2 signal intensity relative to the liver and containing iron deposition. The size of the lesion by MRI was unchanged in comparison with the CT. Eight years later, she presented to the Emergency Room with suprapubic abdominal pain. On CT, she had a large mass (8.3 x 5.5 x 7.1 cm) in the porta hepatis with mass effect upon the gallbladder and pancreas without biliary dilatation or evidence of frank invasion. An FNA was repeated, again showing benign appearing thyroid tissue (bland follicular cells without features of papillary thyroid cancer and abundant colloid). Immunohistochemical staining for TTF-1 was positive, supporting thyroid origin. Thyroid function tests were normal ( TSH-0.85 uIU/mL; free T4 direct- 1.1 ng/dL; and total T3 - 125 ng/dL) There are only three prior case reports detailing ectopic thyroid tissue in the porta hepatis (1). Benign ectopic thyroid tissue in the liver is generally explained as a metaplastic phenomenon, as the thyroid shares a common embryologic origin with the liver and proximal segment of the gastrointestinal tract (2). Workup typically includes CT or US imaging, followed by I-123 imaging to determine the presence of functional thyroid tissue, followed by a biopsy. The prevalence of all ectopic thyroid tissue is 1 per 100,000-300,000 persons, with less than 1% being malignant. The majority (85%) of malignant ectopic thyroid tissue is papillary thyroid cancer. Excision of ectopic thyroid mass in the liver has generally been favored, due to their minor malignant potential. The patient has been referred to Surgical Oncology/Endocrine Surgery for possible resection.