Concurrent occurrence of follicular thyroid carcinoma (FTC) and papillary thyroid carcinoma (PTC) in the same thyroid gland is rare, particularly when presenting initially with distant metastases. We report an elderly female with dual pathology-FTC and papillary thyroid microcarcinoma (PTMC)- with skull metastases as initial manifestation.

We reviewed the clinical presentation, radiologic findings, histopathology, and disease course of an 83-year-old female who presented with right eye blurred vision and a right temporal mass, ultimately diagnosed with metastatic FTC coexisting with PTMC in the thyroid.

An 83-year-old woman presented with a 2-month history of right temporal swelling and progressive blurred vision. MRI revealed a 6.5 × 4.9 × 4.6 cm extra-axial mass at the right sphenoid bone with exophthalmos. Surgical excision confirmed metastatic follicular thyroid carcinoma positive for thyroglobulin, TTF-1, and PAX-8. Thyroid ultrasonography reported bilateral thyroid nodule with malignant feature. Systemic work-up revealed bilateral lung nodules and multiple osteolytic bone lesions. She underwent total thyroidectomy with central lymph node dissection and T8–T10 posterior fusion for pathologic fracture. Pathology demonstrated right follicular thyroid carcinoma (2.8 cm) with capsular and vascular invasion, and left papillary thyroid microcarcinoma (0.1 cm) confined to the thyroid. Postoperatively, she received radioactive iodine ablation (150 mCi), revealing multiple I-131-avid bone metastases and probable pulmonary involvement.

This case illustrates a rare coexistence of FTC and PTMC, emphasizing the importance of thorough histopathologic evaluation in elderly patients with metastatic thyroid carcinoma. Distinguishing between coexistent differentiated thyroid carcinoma subtypes is essential for accurate diagnosis, prognostication, and individualized treatment planning.