Metastasis of a follicular thyroid carcinoma in the frontal sinus

Abstract

Introduction: Follicular thyroid carcinomas (FTC) account for about 10 - 15% of all thyroid carcinomas and are classified as well differentiated carcinomas. Histological differentiation from healthy thyroid tissue is often difficult. Iodine deficiency strumae significantly increase the risk of developing FTC. Haematogenic spread of metastases is possible and occurs primarily into lungs, skeleton, brain and liver. Methods: A patient's case is presented, including the results of imaging procedures. Results: A 61-year-old female patient presented with persistent frontal cephalgia. Due to recurrent goiter, the patient had previously undergone three thyroid resections. An MRI of the head showed a solid tumor of the left frontal sinus. A CT-scan of the paranasal sinuses revealed a bone infiltration towards the anterior cranial fossa and into the left orbital roof. We performed an endoscopic endonasal surgery of the ethmoid and frontal sinus and took tissue samples. The histological examination showed well differentiated thyroid tissue without a clear indication of malignancy. Based on localization, patient's history and clinical findings, a metastasis of an FTC was diagnosed. We performed open surgery of the frontal sinus with removal of the periorbita and duraplasty by the department for Neurosurgery. After resection of the residual thyroid gland a radioiodine therapy was initiated by the department for Nuclear Medicine. Conclusion: Tumors of the paranasal sinuses require swift histological analysis. Rare tumor entities must be considered as differential diagnoses. Due to their often difficult to assess dignity, well differentiated thyroid carcinomas call for thorough interdisciplinary diagnostics, evaluation and therapy.