Objective: To report a case of a patient who developed an acute and transient, tender, and bilateral swelling of the thyroid that occurred during fine-needle aspiration (FNA) of a solitary nodule in the left thyroid lobe; to add accurate ultrasound measurements to support our clinical observation; and to analyze a possible underlying mechanism of this rare condition.
Results and clinical follow-up: The calculated thyroid volume increased from 23 to 57 mL before and at 4 minutes, respectively, after the needle aspiration, but the thyroid volume returned to prediagnostic level after 4 hours. Cytology, serum calcitonin, and histology were concordant, and the nodule was diagnosed as a medullary thyroid carcinoma. Immunohistochemistry was positive for calcitonin, chromogranin, and the very potent vasodilator calcitonin gene-related peptide (CGRP).
Conclusion: This is a rare case of acute and transient thyroid swelling during a common procedure as FNA of a thyroid nodule. This is the first case with documented acute volume expansion quantified by ultrasound measurements supporting our clinical observation, which is in accordance with two historical case reports. The clinical and ultrasound data support the hypothesis of vasodilation as the underlying mechanism, possibly evoked by the release of the vasodilator CGRP.
