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.