Skull metastasis of the clear cell variant of papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC), which is characterized by low incidence of distant metastases, is a common subtype of thyroid carcinoma. Metastases of the clear cell variant (CCV), one of the many PTC variants, are rare. A 73-year-old woman with a 2-year history of a growing subcutaneous tumor in the right temporal region of her skull was admitted to our hospital; the tumor was initially speculated to be meningioma. She was simultaneously being investigated for thyroid mass, which was characterized by abnormal cells with large and atypical nuclei, as well as clear cytoplasm; this mass was considered thyroid cancer according to the result of fine needle aspiration cytology. The patient underwent surgery to remove the temporal mass, which was diagnosed to be skull metastasis of the CCV of PTC. The patient did not receive treatment after being discharged. During the follow-up period, the patient unfortunately passed away eighteen months after the operation. Given that little is known about metastases of the CCV of PTC, we will discuss the pathological and clinical features and further treatment of CCV. Distant metastases of the other PTC subtypes are usual, whereas aggressive behavior of CCV is rarely seen. Notably, the patient was admitted to our hospital because of skull metastasis. However, little is known about the primary focus. We identified the primary tumor through postoperative pathological examination of the skull metastasis. Facing with a skull mass, the clinician and pathologist should consider the possibility of metastasis.