Thyroid nodule is extremely common in clinical practice. An evaluation of thyroid nodule is often straightforward. However, pathologic findings can occasionally be surprising. A 42-year-old previously healthy man was referred to the endocrinology clinic with asymptomatic neck enlargement noted during evaluation of acid reflux symptom. He had no previous radiation exposure to the head and neck. He did not take medication on a regular basis, and denied smoking cigarettes or drinking alcohol in excess. Family history was unremarkable for thyroid disease or cancer.
Assessment
Salient physical examination revealed a visible, soft, painless thyroid mass of approximately 6 cm within the gland. Ultrasonography of the thyroid gland identified a large complex nodule measuring 6.6 × 4.5 × 3.3 cm with central internal blood flow that occupied almost the entire left thyroid lobe (Figure 1). The right lobe of the thyroid measured 4.9 × 1.6 × 1.1 cm and the left thyroid lobe measured 6.9 × 4.9 × 3.8 cm without other thyroid nodules. Thyroid-stimulating hormone was 3.79 U/mL (ref 0.4-4.0 U/mL).
Ultrasound-guided fine-needle aspiration of the left thyroid nodule was performed. A cytology examination reported a benign nodule (Figure 2). Given the large-size nodule, surgical removal was recommended. The patient underwent left thyroid lobectomy and isthmusectomy. Intraoperatively, the thyroid gland was hypervascular, with very large blood vessels. The procedure was complicated with transient left vocal cord apraxia and subclinical hypothyroidism requiring thyroid replacement postoperatively.
Surgical pathology revealed a 6.8-cm partially encapsulated tumor with a thin rim of normal thyroid. Gross finding of the tumor revealed a red tan tissue that was surrounded by a capsule. Microscopically, the tumor was arranged in an organoid vascularized pattern, with Zellballen architecture comprised of central cells with often highly pleomorphic enlarged nuclei and abundant eosinophilic and vacuolized cytoplasm, surrounded by spindle sustentacular cells (Figure 3). Immunohistochemical stains of the specimen were positive for chromogranin, synaptophysin in organoid neoplastic cells, and S100-highlighted sustentacular cells (Figure 4). There was focal weak positivity of Pax8. Ki67 labeled approximately 5% of tumor cells. No expression of cytokeratin, thyroid transcription factor 1, parathyroid hormone, thyroglobulin, or calcitonin was identified in the tumor cells. Three lymph nodes were negative for malignancy. These findings were consistent with paraganglioma.
To read this article in its entirety please visit our website.
-Jutarat Sangtian, MD, Maria Rae Evasovich, MD, Tasma Harindhanavudhi, MD
This article originally appeared in the April 2017 issue of The American Journal of Medicine.
