Oncocytoma of the parotid gland causing false-positive result on I-131 whole-body scintigraphy.

A 50-year-old patient underwent near-total thyroidectomy in 1997 because of a T₁N₀M₀ follicular carcinoma in the right lobe of the thyroid gland, followed by I-131 ablation (3700 MBq). Follow-up of I-131 whole-body scintigraphy after 9 years showed pathologic uptake at the left side of the neck. Histopathologic analyses of the resected specimen suggested a cystic metastasis within the parotid gland, probably originating from thyroid carcinoma. However, the patient had been disease-free for over 9 years and thyroglobulin was undetectable in plasma. Revision of the specimen with complementary immunohistochemical staining revealed histopathologic aspects more typical of oncocytoma.