Parasitic nodule of the thyroid in a patient with Graves' disease

We report a case of a parasitic nodule of the thyroid in a patient with Gra ves' disease, which mimicked a lymph node metastasis from a primary occult thyroid carcinoma. The patient was a 67-year-old Japanese woman with a past history of subtotal thyroidectomy for Graves' disease, who was referred to our hospital because of a right cervical mass. A lymph nodelike lesion mea suring 1.5 cm in diameter was palpable, distinct from the remnant of the ri ght thyroid lobe. Thyroid scintigraphy using I-123-Na revealed a hot lesion at the upper lateral portion of the right thyroid lobe, and this was resec ted. Microscopically, the mass showed thyroid follicles with lymphocytic in filtration and lymphoid follicles. Clear ground glass nuclei, nuclear groov ing and intranuclear inclusions were not observed. No morphological evidenc e of the lymph node was found in the mass by reticulin staining. Parasitic nodules of the thyroid in patients with Graves' disease may mimic a metasta tic carcinoma of the thyroid.