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Background
Primary intraventricular neoplasms are rare tumors that originate from the ependymal or subependymal, septum pellucidum, choroid plexus, and the supporting arachnoid tissue.

Educational Goals / Teaching Points
We report a series of primary intraventricular tumors (IVTs) treated in a tertiary teaching hospital in Singapore. The imaging features of IVTs are correlated with the surgical approaches to the ventricular system. Here, we comprehensively outline the imaging characteristics, pathology, and surgical approaches for various primary IVTs.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Subependymoma is a well-defined lesion with calcification on CT, and a T1 iso- and T2 hyperintense, hypoenhancing lesion on MRI, most commonly located in the lateral and third ventricle. It is a slow-growing, WHO grade I tumor arising from subependymal cells. Surgical approach is frequently gross total resection (GTR), with an aim to relieve hydrocephalus. Ependymoma demonstrates heterogeneous signal intensities and enhancement with cystic/necrotic areas, most commonly located in the posterior fossa. It arises from ependymal lining of the ventricles, WHO grade II or III. Surgical approach is frequently suboccipital craniotomy and careful tumor resection sparing the cranial nerves. Central neurocytoma is well-defined with peripheral calcifications and a “soap bubble appearance” on T2-weighted MRI. It is a well-differentiated tumor, WHO grade II, in close contact with the septum pellucidum. Surgical approach is frequently transcallosal endoscopic assisted resection. Choroid plexus tumor is an enhancing lesion with a “cauliflower” appearance, most commonly located in the ventricular atrium, fourth ventricle, and may obstruct CSF pathways. It arises from choroid plexus epithelium and has different histological types (papilloma, carcinoma). Surgical approach is frequently GTR to treat hydrocephalus. Meningioma is a well-defined lesion with variable enhancement and signal intensities, most commonly located in the ventricular trigone. It arises from arachnoid cap cells and is usually benign (WHO grade I). Surgical approach depends on tumor location and size, preferably GTR. Colloid cyst is hyperintense on T1W MRI, and often obstructs the foramen of Monro. It is a gelatinous cyst lined with cuboidal or columnar epithelium. Surgical approach is usually endoscopic fenestration, piecemeal removal, aiming to relieve hydrocephalus.

Conclusion
We highlight the importance of recognizing the key imaging features of primary IVTs for accurate diagnosis and treatment planning. The choice of surgical approach depends on tumor location, size, and extension. Complete tumor resection is advocated in most cases. Advances in neuroendoscopy have expanded treatment options, allowing for minimally invasive procedures in certain cases. The radiologist's expertise in identifying these characteristics aids in diagnosis and guides therapeutic decisions to improve patient care.