A 58-year-old man comes to the office for evaluation of a thyroid nodule. The patient first noticed a painless neck lump 2 months ago, which has progressively enlarged. He has had no heat or cold intolerance, recent weight changes, or difficulty breathing or swallowing. Medical history is notable for well-controlled hypertension. The patient has no history of radiation exposure or family history of thyroid diseases. Physical examination shows a firm, nontender nodule in the right thyroid lobe. Serum TSH level is normal, and ultrasonography shows a 4-cm solid nodule in the right thyroid lobe. Fine-needle aspiration biopsy shows a large number of follicular cells dispersed in clusters and microfollicles. The patient undergoes right thyroid lobectomy. Which of the following histologic findings would confirm a diagnosis of follicular thyroid carcinoma in this patient?

Question

A 58-year-old man comes to the office for evaluation of a thyroid nodule.  The patient first noticed a painless neck lump 2 months ago, which has progressively enlarged.  He has had no heat or cold intolerance, recent weight changes, or difficulty breathing or swallowing.  Medical history is notable for well-controlled hypertension.  The patient has no history of radiation exposure or family history of thyroid diseases.  Physical examination shows a firm, nontender nodule in the right thyroid lobe.  Serum TSH level is normal, and ultrasonography shows a 4-cm solid nodule in the right thyroid lobe.  Fine-needle aspiration biopsy shows a large number of follicular cells dispersed in clusters and microfollicles.  The patient undergoes right thyroid lobectomy.  Which of the following histologic findings would confirm a diagnosis of follicular thyroid carcinoma in this patient?

Quizplus · Accepted Answer

11ec160b_391a_edac_9249_95e3f53ed56b_MD0001_00 This euthyroid patient has a slowly enlarging, firm, painless thyroid nodule and fine-needle aspiration (FNA) results indicative of a follicular neoplasm (eg, numerous follicular cells and microfollicles). Most follicular thyroid neoplasms are benign follicular adenomas, but 15%-30% can be malignant follicular carcinomas. Both types of follicular neoplasms have a similar appearance on ultrasound and FNA. Differentiating between benign and malignant follicular lesions can only be accomplished by histologic examination of the entire tumor (eg, thyroidectomy). This propensity of follicular thyroid carcinomas to invade surrounding blood vessels accounts for their tendency to metastasize via hematogenous spread to distant tissues (eg, bone, lung). (Choice A) Medullary thyroid carcinomas can develop sporadically or in patients with an inherited RET proto-oncogene mutation (eg, multiple endocrine neoplasia 2a or 2b). In patients with this germline mutation, C-cell hyperplasia is often found as a precursor to a malignant lesion. Malignant C cells secrete calcitonin, which can form amyloid deposits within the tumor. (Choice B) Papillary thyroid carcinoma (the most common type of thyroid malignancy) has distinct cytologic and histologic features. These include laminar calcifications (psammoma bodies), large cells with pale, empty-appearing nuclei (Orphan Annie-eye or ground-glass nuclei) with nuclear inclusion bodies and nuclear grooves. Unlike FTC, papillary thyroid carcinoma can be diagnosed on FNA results. (Choice C) Hürthle cells are large, polygonal cells with granular, eosinophilic cytoplasm due to large quantities of mitochondria. They are a nonspecific finding seen in a wide variety of neoplastic and nonneoplastic thyroid lesions. Therefore, they would not be of benefit in differentiating between benign and malignant follicular lesions. (Choice D) Chronic autoimmune (Hashimoto) thyroiditis typically presents with signs of primary hypothyroidism (eg, weight gain, cold intolerance, elevated TSH) due to autoimmune destruction of the thyroid gland. Histology shows inflammation and lymphocytic germinal centers in the thyroid gland. (Choice E) Multinucleated giant cells are seen in many thyroid conditions, including thyroiditis, cystic degeneration, and papillary thyroid carcinoma. They are not typically seen in follicular lesions. Educational objective: Follicular neoplasms typically present as slowly enlarging, painless thyroid nodules. Differentiation between a follicular adenoma and follicular thyroid carcinoma is not possible using only fine-needle aspiration results. Histologic evidence of invasion of the tumor capsule and/or surrounding blood vessels is needed to diagnose follicular thyroid carcinoma.

A 58-Year-Old Man Comes to the Office for Evaluation of a Thyroid