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Colloid cysts are benign tumors. They commonly arise from the roof of the third ventricle (from a structure called the paraphysis), and are rarely seen in the lateral ventricle. They were first described in 1858 at autopsy. Walter Dandy performed the first successful resection in 1921.
These tumors are rare with an incidence of 0.2-2% of all intracranial tumors. There is a slight male preponderance. They may occur at any age (typically in adults), but mean age at presentation is generally around 40 years of age (range from a large series 17-72 years).
Patients may present clinically, frequently with headaches, or the lesions may be found incidentally in asymptomatic patients. Ataxia and vertigo may also be associated with symptomatic colloid cysts.
ImagingOn non contrast CT, they may be difficult to identify, but may also be slightly hyperdense. On MRI they are often bright on T1 weighted imaging and may or may not contrast enhance.
These lesions are encapsulated and contain a gelatinous, colloid material within them.
They are marked by a single layer of colmnar epithelial cells, and may contain goblet and ciliated cells. The cyst fluid is amorphous ad brightly eosinophilic. Filamentous-like masses of nucleoprotein may be seen. They are positive for EMA and cytokeratin markers by immunohistochemistry.
Treatment for incidental or mildly symptomatic colloid cysts is controversial. Criteria for treatment include symptomatic lesions or lesions greater than 1 cm or with associated hydrocephlus. The risk of sudden death from symptomatic lesions is as high as 35% and is generally thought to occur from sudden obstructive hydrocephalus.
Open microsurgical resection has been used with success for treatment for many years. Standard approaches include a transcortical approach (with increased risk of seizure) or Transcallosal approach (with risk of injury to the pericallosal arteries or fornix). Endoscopic resection is gaining more popularity but requires significant facility with endoscopic techniques. Aspiration of the cyst provides only temporary relief as the recurrence rate is high.
With complete resection, recurrence rates are low. These are benign tumors and there is essentially no malignant potential. With aspiration only, the recurrence rates are high.