PMC9062956_01
Noncontrast axial CT image demonstrates heterogeneously hyperdense mass within the septum pellucidum (a). Axial T2-weighted MRI image demonstrates location of the hemorrhagic lesion posterior to the columns of the fornix within the cavum vergae (b). Coronal (c) and sagittal contrasted T1-weighted MRI images demonstrate patent foramen of Monro (d) lateral displacement of internal cerebral veins (e) and thalami bilaterally.
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F1
However, initial CT imaging of the head revealed a heterogeneously hyperdense, lobulated mass in the area of the posterior septum pellucidum measuring 2.8 cm in diameter without any evidence of hydrocephalus [Figure 1a]. A subsequent MRI demonstrated a hemorrhagic mass lesion within the cavum vergae [Figure 1b], posterior to the columns of fornix and foramen of Monro [Figures 1c and d], and displacing the internal cerebral veins laterally. The contour of the mass was irregular, with asymmetric extension posteriorly and inferiorly, resulting in mass effect on the thalami bilaterally [Figure 1e].
Colloid cyst displaced the fornices laterally and did not extend into the 3rd ventricle (a). Xanthochromic, mucinous contents of the colloid cyst (b). Adherence of the cyst wall to the internal cerebral vein (c). 3V: 3rd ventricle, CC: Colloid cyst, F: Fornix, and ICV: Internal cerebral vein.
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F2
It displaced the fornices laterally but did not extend into the third ventricle [Figure 2a]. The cyst contained xanthochromatic and mucinous debris with evidence of recent as well as chronic hemorrhage [Figure 2b]. The capsule was densely adherent to bilateral internal cerebral veins, requiring careful microsurgical dissection [Figure 2c].
Periodic acid-Schiff stain of cavum vergae colloid cyst, which is lined with sparsely ciliated, simple cuboidal cells (a). Cholesterol clefts were also present (b).
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F3
On pathology, the cyst was found to be lined by a simple layer of cuboidal cells which were sparsely ciliated and diffusely positive for epithelial markers epithelial membrane antigen and cytokeratin [Figure 3].