A case who presented as isolated calvarial metastases in the form of scalp swelling and mimicked a meningioma. A 60-year-old female, a known case of goiter with hypothyroidism for 10 years and receiving Eltroxin, presented to the neurosurgery outpatient department with a complaint of left-sided scalp swelling measuring 11 cm × 9 cm, associated with headache and generalized weakness. There was no history of nausea and vomiting. Higher mental functions and cranial nerve examination were with normal limits. All the baseline investigations were within normal limits. Contrast-enhancing magnetic resonance imaging and computed tomography angiography showed left frontal calvarial mass approximately measuring 10 cm × 8 cm in size. Fine-needle aspiration cytology was done from the scalp lesion, and it was suggestive of secretory meningioma. In view of clinical and imaging findings, preoperative diagnosis of the left frontal calvarial metastases was made with differential of meningioma. Intraoperative, a tumor was identified extending from dura to both frontal bone and anterior part of the left parietal bone and causing destruction of bone. Gross total excision of the tumor was done followed by duraplasty.

On microscopy, a tumor was seen arranged in the form of well-formed back to back arranged follicles filled with colloid-like material. These tumor cells were moderately pleomorphic with round-to-oval nuclei, inconspicuous nucleoli, and moderate cytoplasm. These tumor cells were suspicious of follicular carcinoma of the thyroid. Tumor cells were seen infiltrating through the dura mater and bone Thyroid origin was confirmed by positive immunohistochemistry for thyroid-associated antigens, i.e., thyroglobulin and thyroid transcription factor-1, confirming the diagnosis of metastatic thyroid carcinoma. Based on histopathology report, ultrasonography of the thyroid gland was done and it was suggestive of malignant lesion. Fluorodeoxyglucose (FDG) positron emission tomography scan did not show any FDG-avid lesion anywhere in the body. Postoperative period was uneventful, the patient was planned for thyroid surgery ¹⁾