CNSM-06 WHEN BRAIN LESIONS AREN’T WHAT THEY SEEM: THE POWER OF COMBINING MRI AND RADIOACTIVE IODINE SCINTIGRAPHY FOR THYROID CANCER IN A RESOURCE-LIMITED SETTING

Abstract

Abstract Background and Aims Accurate imaging is essential for the diagnosis, staging, and treatment planning of cancer. Magnetic Resonance Imaging (MRI) provides high-resolution anatomical detail and is preferred for evaluating intracranial lesions, while radioactive iodine (RAI) scintigraphy remains the cornerstone of functional imaging (and therapy) in well-differentiated thyroid cancer (WDTC). These modalities offer complementary insights, which are particularly valuable in resource-limited settings where hybrid imaging may be unavailable. This case report demonstrates the utility of combining MRI and RAI scintigraphy to improve diagnostic accuracy in a patient with suspected intracranial metastases from follicular thyroid cancer (FTC). Methods We retrospectively reviewed the clinical records and imaging findings (MRI and RAI scintigraphy) of a 51-year-old Nigerian woman with advanced FTC. Independent and integrated image interpretation was performed, followed by histopathological correlation. Results The patient presented with progressive right-sided exophthalmos and underwent brain MRI, which revealed a right sphenoid wing mass extending into the orbit. Initial postoperative histology suggested polymorphous low-grade adenocarcinoma, but immunohistochemistry favoured metastatic FTC. Two additional enhancing intracranial lesions were interpreted as likely benign epidermoid cysts. However, whole-body RAI scintigraphy subsequently demonstrated abnormal cranial uptake spatially congruent with the locations of these lesions, raising suspicion for metastatic disease. Surgical excision and histology confirmed the diagnosis of metastatic FTC. Conclusions Accurate staging is critical in advanced thyroid cancer, particularly when intracranial metastases are present, as these represent a contraindication to radioactive iodine therapy (RAIT) without prior surgical resection. In this case, RAI scintigraphy proved vital in reclassifying lesions initially presumed benign, thereby preventing potential complications such as cerebral edema, increased intracranial pressure, and seizures following RAIT. This case underscores the importance of combining functional and anatomical imaging to enhance diagnostic precision, especially in resource-constrained settings where hybrid imaging technologies are limited but can be effectively simulated through multimodal integration.