Choroid plexus tumors

Epithelial tumors of the choroid plexus

Choroid plexus papilloma (Choroid Plexus Papilloma). It is a neoplasm that visualizes on magnetic resonance imaging as a lobulated (lobulated) mass. The typical anatomical localization of this lesion is the atrium of the lateral ventricle. Upon intravenous administration of a paramagnetic contrast agent on T1-weighted images with gadolinium, intense, marked contrast enhancement is observed. Due to impaired normal cerebrospinal fluid circulation, the disease is almost always accompanied by dilation of the ventricular system driven by associated hydrocephalus.

Choroid plexus carcinoma (Choroid plexus carcinoma). Classified as an extremely rare but highly malignant neoplasm. The main distinguishing imaging and pathomorphological feature of carcinoma lies in its aggressive infiltrative growth: it invades the adjacent brain parenchyma to a significantly greater extent than papillomas, blurring the natural anatomical boundaries between the ventricular lumen and the brain parenchyma.

Colloid Cyst

It is a specific space-occupying lesion with a strictly defined anatomical localization. It occurs exclusively in the paraphysis region, which corresponds to the posterior lip of the interventricular foramen of Monro (the narrow space between the third ventricle and the anterior horns of the lateral ventricles).

Clinically and radiologically, these smooth, spherical lesions tend to cause hydrocephalus. This occurs due to intermittent (the so-called ball-valve mechanism) or continuous obstruction of the cerebrospinal fluid (CSF) outflow pathways from the lumen of the lateral ventricles, leading to their enlargement.

Diagnostic imaging of a colloid cyst:

• Computed tomography (CT): On unenhanced scans (without contrast), spontaneous hyperattenuation is typical for the cyst.
• Magnetic resonance imaging (MRI): Signal characteristics are extremely variable as they directly depend on the biochemical composition of the cyst contents (concentration of calcium salts, cholesterol crystals, hemosiderin pigment). In some cases, the MR signal may be completely similar to CSF, but a hyperintense signal on T2-weighted images and in T1 FLAIR mode is significantly more common. On FLAIR mode, the cyst is visualized as a well-circumscribed lesion with a homogeneous bright signal (due to thick proteinaceous contents).
• Contrast enhancement: Unlike solid tumors, a colloid cyst does not enhance with contrast and remains isointense on post-contrast T1-weighted images.

Intraventricular Meningioma

In patients older than 10 years, meningioma is the most common cause of a space-occupying lesion in the anatomical zone of the lateral ventricle atrium.

Morphologically, it is a well-circumscribed, globular (rounded) mass. The imaging appearance on CT and MRI is entirely similar to typical extraventricular meningiomas:

• CT: The lesion usually appears moderately to markedly hyperdense.
• MRI: On T1- and T2-weighted images, the signal intensity of the meningioma tissue is isointense and completely similar to the normal signal from the cerebral cortex.
• Contrast enhancement: The tumor demonstrates pronounced, intense, and homogeneous contrast enhancement on both CT and MRI.

Central Neurocytoma

When analyzing the clinical patterns of intraventricular masses, central neurocytoma must be highlighted. This lesion is anatomically always closely associated with the septum pellucidum (septum pellucidum).

On MR images, neurocytoma presents as a partially cystic, multilocular (having multiple internal septa — multi-septated) space-occupying lesion that actively enhances with contrast. The tumor is capable of filling the bodies of both lateral ventricles, inevitably causing secondary hydrocephalus (on scans, this frequently manifests as marked dilation of the temporal horns of the lateral ventricles).

General principles for evaluating intra-axial tumors

Although intraventricular lesions have their specific features, it is important to remember the general rules for evaluating intra-axial (Intra-axial Tumours) brain tumors:

1. Role of contrast enhancement: Contrast enhancement in intracerebral tumors helps characterize the internal structure of the lesion and determine its borders. However, the presence or absence of contrast enhancement by itself is not a reliable and unambiguous predictor of the grade of malignancy.
2. WHO Classification (2016): Key DNA mutations are integrated into the final diagnosis as critical prognostic factors (the modern concept of "layered diagnosis" or layered diagnosis).
3. Molecular genetics: To determine the specific subtype of glial tumors, the main genetic determinants to date are the IDH gene mutation status and the presence of 1p/19q chromosomal co-deletion.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Differential diagnosis of space-occupying lesions of the lateral ventricle atrium.
• The role of IDH mutations and 1p/19q co-deletion in the WHO (2016) "layered diagnosis" concept.
• Pathophysiology and imaging features of obstructive hydrocephalus in tumors of the foramen of Monro.
• MR semiotics of extraventricular meningiomas compared to intraventricular forms.
• Imaging anatomy of the structures of the interventricular foramen of Monro and the paraphysis.

Other topics in the Neuroimaging section

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