Squamous cell carcinoma in a thyroglossal duct cyst and 99mTc-MIBI findings.

: The incidence of carcinomas in thyroglossal duct cysts is extremely low. The vast majority are papillary carcinomas, with only 14 cases of squamous cell carcinomas reported in the literature. A 78 years old male patient presented with an asymptomatic large mass in his anterior neck, considerably immobile, with inflamed overlying skin. Imaging studies confirmed the cystic nature-doughnut shape of the lesion, giving evidence of malignant infiltration of the surrounding tissues, without lymph node enlargement. Fine needle aspiration was positive for a possible squamous cell malignancy. A wide Sistrunk procedure was performed and the mass was excised along with the strap muscles and the infiltrated overlying skin. Histopathology confirmed the diagnosis of a moderately differentiated squamous cell carcinoma. In conclusion, scintigraphy with (99m)Tc-MIBI showed the characteristic doughnut sign. The rarity of this diagnosis along with differential diagnosis dilemmas are the key points of this presentation.