Vascular proliferation of the thyroid. A complication of fine-needle aspiration.

Fine-needle aspiration (FNA) of the thyroid has a low morbidity rate, with hematoma formation being the most commonly encountered complication. We describe two cases of exuberant vascular proliferation within the thyroid gland, one resembling a cavernous hemangioma and the other with similar changes but with areas of papillary endothelial hyperplasia. Both lesions occurred in patients with a recent history of FNA prior to the thyroidectomy procedure. The vascular proliferation was interpreted as organizational changes in a hematoma secondary to the FNA. These cases, in conjunction with a recent case of Masson's vegetant intravascular hemangioendothelioma complicating thyroid FNA, expand the literature on vascular proliferations that may develop subsequent to thyroid FNA.