Metastatic follicular thyroid carcinoma masquerading as olfactory neuroblastoma: with skull-base, cranium, paranasal sinus, lung, and diffuse bone metastases.

Skull-base metastasis is rarely reported in thyroid carcinoma. We are presenting an unusual interesting case mimicking metastatic renal cell carcinoma with intense clear cell morphology, the thyroid origin of which was detected via positron emission tomography/computerized tomography scan proposed by the oncology council, while we were monitoring the subject with the initial diagnosis of paranasal sinus tumor. A mass was detected in the left nasal cavity in the endoscopic examination of the 68-year-old female patient referred by the ophthalmology clinic with the preliminary diagnosis of retro-orbital tumor upon being admitted with proptosis. A soft tissue lesion at a size of 68 × 39 × 53 mm located intracranially was detected by the brain computerized tomography. The biopsy taken and the immunohistochemical results were not satisfactory. Intense fluorodeoxyglucose involvement was observed in both lobes of the thyroid gland at positron emission tomography/computerized tomography taken with the recommendation of the council. Moreover, hypermetabolic nodules were seen in both lung parenchyma areas, whereas intense hypermetabolic lytic lesions were observed in the skeletal system. Thyroglobulin and thyroid transcription factor 1 stains displayed a strong staining on paraffin block. On the basis of these characteristics, the case was regarded as compatible metastatic follicular thyroid carcinoma, with skull-base, cranial, retro-orbital, paranasal sinus, lung, and bone metastases. This case showed us that multidisciplinary work and assessment of the oncology council play a highly critical role in making the diagnosis and guiding the treatment.