Thyroid nodule with arteriovenous malformation: under-recognized cause of increased vascularity.

Background: Head and neck arterio-venous malformations (AVM) are not frequent lesions and no thyroid cases have been reported to date; as hypervascular nodular lesions, they can be misdiagnosed as malignant.

Findings: We present two patients with palpable thyroid nodules with suspicions of malignancy based on the hypervascular imaging findings. Histologically, these lesions were well-defined adenomatous nodules with multiple interconnected blood vessels of variable size, many of them dilated and arranged predominantly at the periphery of the lesions. These findings characterize thyroid AVM in the background of adenomatous nodules. Age-matched euthyroid benign non-infiltrative follicular lesions without vascular component, adenomatous hyperplastic nodules (37) and follicular adenomas (21), during the same period (2 years) were retrieved to evaluate vascular markers. Compared with the non-nodular tissues and controls, the hyperplastic nodules with vascular malformation displayed significant mRNA overexpression for VEGF-A, PDGF-A, PDGF-B, and eNOS.

Conclusions: Vascular lesions of thyroid gland are rare and they can present as palpable nodules revealing well-defined edges, zonal blood vessel distribution and up-regulation of VEGF-related pathway and eNOS. These findings can help identify the true nature of these lesions.