Purpose or Case Report: In our case series, we highlight the imaging findings of two patients with rare “neuroblastoma” tumors in which the diagnosis was not considered preoperatively, emphasizing the importance of pediatric radiologists being aware of these unusual etiologies for accurate diagnosis and management.

A 17-year-old with blurry vision presented with progressive visual deterioration. MRI revealed a 5.5 cm mass in the inferior left frontal lobe, impacting the prechiasmatic optic nerve and optic chiasm. A CTA confirmed the lesion's encasement of the circle of Willis's left aspect. The patient underwent a craniotomy for tumor resection, revealing a primary CNS neuroblastoma FOXR2-activated, WHO grade 4.

Another patient, a 13-year-old female, reported vomiting, abdominal pain, and diarrhea. The past medical history included Lyme disease and "cat scratch" fever. Severe hyponatremia was discovered, initially attributed to viral sequelae, necessitating prolonged hospitalization. An incidental nasal cavity/maxillary sinus "polyp" was identified and excised, diagnosed as olfactory neuroblastoma (Esthesioneuroblastoma), Hyam grade 3, Kadish stage 2. Post multiple surgeries and radiation, the hyponatremia, a result of SIADH, resolved with tumor treatment.

Neuroblastomas, typically arising from the adrenal gland or retroperitoneum, are the most common extracranial solid pediatric tumors. They are usually sporadic, but sometimes associated with specific syndromes. Primary intracranial neuroblastomas are rare, with ambiguous classification and no distinct imaging characteristics or established adjuvant treatment protocols, contributing to high recurrence rates. CNS neuroblastomas more commonly affect the spine, with intracranial instances being rare but important differential diagnoses for pediatric brain tumors.

Similarly, esthesioneuroblastomas, originating from olfactory neuroepithelial cells, are rare, constituting only 0.6% of all upper aerodigestive tract tumors. Ectopic cases are even rarer, with some inducing paraneoplastic syndromes like ectopic Cushing’s or SIADH. Particularly, esthesioneuroblastomas with SIADH-related euvolemic hyponatremia have a mere 2% prevalence and should be considered in atypical/refractory hyponatremia cases with incidental sinus masses.
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