A 77-year-old man underwent fine needle aspiration biopsy of a 3.5 cm nodule of the right thyroid lobe. Cytology showed small cells with scant cytoplasm; on immunocytochemistry, the cells showed high proliferative activity and cytoplasmic expression for neuroendocrine marker synaptophysin. These findings were suggestive for a small cell carcinoma of the thyroid gland. Therefore, the patient underwent fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG PET/CT) for staging. PET/CT showed an area of increased F-18-FDG uptake corresponding to the right thyroid nodule (Fig. 1a, b). Furthermore, an area of increased radiopharmaceutical uptake was detected in the brain, corresponding to a lesion located in the left parietal lobe on low-dose CT (Fig. 1a, c). Biopsy of the brain lesion was suggestive for small cell carcinoma. The final diagnosis based on pathology and F-18-FDG PET/CT findings was small cell carcinoma of the thyroid gland with brain metastasis. The patient was addressed to chemotherapy and radiation therapy, but he died 6 months after the begin of therapy for disease progression.
Small cell carcinoma is a very aggressive neuroendocrine tumour usually arising from the lung, but the primary site may be rarely and virtually located in any organ [1, 2]. Previous reports demonstrated that F-18-FDG PET/CT could provide relevant information in staging patients with small cell carcinoma located in different anatomical sites [1, 2]. Furthermore, F-18-FDG PET/CT has been demonstrated to be a useful imaging technique in aggressive thyroid tumours , providing useful information about staging, restaging and prognosis.
To the best of our knowledge, our case is the first in the literature which evaluated a metastatic small cell carcinoma of the thyroid gland by F-18-FDG PET/CT. In our case this functional imaging method has been very useful in correctly staging this rare aggressive thyroid tumour.
Conflict of interest
The authors declare that they have no conflicts of interest.