Two Cases of Thyroid Metastasis from Head and Neck Squamous Cell Carcinoma Detected by FDG-PET/CT

Intrathyroidal metastasis of tonsillar squamous cell carcinoma masquerading as a primary thyroid tumor

Intrathyroidal metastasis of tonsillar squamous cell carcinoma is rare. To date, only six cases have been reported in the literature. This case was unusual and presented with thyromegaly before the diagnosis of the primary tumor. A 55-year-old male patient was suspected to have a primary thyroid tumor with nodal metastasis. The thyroid gland was diffusely enlarged, with no discernible mass. Histologically, the thyroid parenchyma revealed extensive endolymphatic tumor emboli, which were positive for p40 and p16 in a background of chronic lymphocytic thyroiditis. Positron emission tomography-computed tomography revealed hypermetabolic activity in the right tonsillar region. Tonsillar biopsy revealed human papillomavirus-positive squamous cell carcinoma. The present case is the first reported case of intrathyroidal metastasis of tonsillar squamous cell carcinoma with an initial clinical presentation of thyroid enlargement before the primary tumor of tonsillar cancer was diagnosed.

Role of Imaging in Clinically Occult Isolated Intrathyroidal Metastasis from Squamous Cell Carcinoma of Tongue: An Unusual Case Series

Metastasis to the thyroid gland is rare; furthermore, intrathyroid metastasis from head and neck squamous cell carcinoma (SCC) is very unusual, with only nine previously documented cases four from intrathyroid metastasis from nasopharyngeal carcinoma, two from oral cavity, one each from oropharynx, larynx, and parotid. The reported case series are unique in nature and illustrates the role of fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) and ultrasound-guided biopsy in diagnosing clinically occult isolated intrathyroidal metastasis, which helps in the best management for an isolated intrathyroid metastases. This study details the cases of three patients who were diagnosed with intrathyroidal metastasis from SCC of the tongue by PET-CT, followed by USG-guided biopsy, who were treated with either surgery and or chemotherapy. Although intrathyroidal metastasis is an uncommon occurrence and signifies poor prognosis, early detection of an isolated intrathyroidal metastasis on imaging in an appropriately selected patients, radical surgery, and/or chemotherapy improve local control and quality of patient's life.