Pathologically, the cyst wall was made of mono-/multilayered ciliated cuboidal epithelium with focal pseudostratifications. There were randomly distributed goblet cells that were full of glycoprotein in periodic acid Schiff pretreated with diastase (PAS/PASD), and showing cytoplasmic acid mucopolysaccharides collection in PAS-AB (Fig. 4A and B). Gomori stain showed dense reticulum fibers in the cyst wall, and hyalinized connective tissue was present on the outer side of the cyst wall. The cyst content was consistent with colloid cyst (Fig. 4C) Immunohistochemical examination was performed using glial fibrillary acidic protein (GFAP), epithelial membrane antigen, ki-67, synaptophysin, p53, CK7, CK-20, and S-100 antibodies of which only epithelial membrane antigen was found to be positive (Fig. 4D). The presence of normal adenohypophysis was present.
Patient was started on oral desmopressin treatment due to diabetes insipidus developed on the postoperative third day and continued to use for 2 months until the resolution of the complication. A control MRI obtained 5 months after the operation demonstrated neither recurrence nor residue of the colloid cyst (Fig. 3).
Colloid cysts are rarely seen intracranial lesions usually located within the ventricular system, particularly the third ventricle. Extraventricular involvement is uncommon and few patients for a specific localization were reported in the literature.1 Although they were included in patient series involving the sellar region in the literature, the histologic criteria were not defined to establish the diagnosis as was the only clinical report by Bladowska.3,4
Although pathological definition is not simple, the histopathologic examination remains the standard diagnostic method. Colloid cysts have an outer fibrous capsule and an inner lining of a single layer of squamous, cuboidal, or columnar ciliated, or nonciliated epithelium. The cyst consists of gelatinous material that reacts positively to PAS staining.2
Computed tomography and MRI can be used in diagnosis of colloid cysts. On CT images the lesion is usually seen as hyperdense or rarely as hypodense or isodense. The MRI findings depend on the composition of the cyst content, that is, cerebrospinal fluid like or mucous cyst content. Approximately half of the cysts are hyperintense on T1-weighted images, whereas T2-weighted images are variable. Colloid cysts do not show enhancement even in the cyst wall.3 In our patient, the lesion was uniformly isointense on T1- and profoundly hypointense in T2-weighted sequences. Contrast enhancement was not seen throughout the lesion including the cyst wall.
In contrast to ventricular localization where most of the colloid cysts originate from, the differential diagnosis from other cystic lesions of the sellar region such as RCC, arachnoid cyst, cystic pituitary adenoma, craniopharyngioma, empty sella, pituitary necrosis, or hypophysitis is challenging.1,3
Among these lesions RCCs deserve a special attention since they imitate colloid cysts both histopathologically and radiologically. Rathke cleft cysts sporadically show squamous metaplasia, a finding never observed in colloid cysts and stain positively for GFAP and skin type keratin,5 whereas colloid cysts do not. Our patient did not show a positive staining pattern with GFAP, keratin 7, and keratin 20. Another discriminating feature is that capsule of the RCCs tends to be thicker than colloid cysts.1,5 Finally, RCCs containing mucoid fluid are indistinguishable from colloid cysts whereas serous RCCs exhibit cerebrospinal fluid signal intensity on all MR sequences.3
Bender et al3 reported a series of 38 patients with sellar cystic lesions to discriminate sellar colloid cysts from RCCs and found hyperintense T1 signal or mixed T2 signal with focal areas of hypointensity (dot sign) in majority of colloid cysts consistent with previous reports. All RCCs showed wall enhancement compared with colloid cysts with a sensitivity of 100% and specificity of 93%. They also demonstrated that RCCs had more prominent suprasellar extension.3
Radiologic images of the colloid cysts can be helpful in treatment planning. The hyperdense appearance on CT or a hypointense appearance on T2-weighted MRI is a result of viscous ingredient and would suggest that stereotactic aspiration would be ineffective.3
The management of these cysts includes cyst aspiration, microsurgical, and more recently endoscopic resection. Simple decompression of the cyst content without the removal of the cyst wall often results in recurrence in third ventricular colloid cysts. Recently, there has been increased interest in endoscopic approaches to minimize postoperative complications.1 We resected the lesion microsurgically through a transnasal transsphenoidal approach in our patient with no recurrence in follow-up.
We report a patient of pituitary colloid cyst successfully removed through the transnasal transsphenoidal approach. Although rarely found in this location colloid cysts should be considered in the differential diagnosis in patients who present with a pituitary cystic lesion.
1. Laidlaw J, Kaye AH. Kaye AH, Laws ER. Colloid cysts. Brain Tumors: An Encyclopedic Approach
. New York: Churchill Livingstone, London; 2012. 849–863.
2. Lach B, Scheithauer BW, Gregor A, et al. Colloid cyst of the third ventricle. A comparative immunohistochemical study of neuraxis cysts and choroid plexus epithelium. J Neurosurg
3. Bender B, Honegger JB, Beschorner R, et al. MR imaging findings in colloid cysts of the sellar region: comparison with colloid cysts of the third ventricle and Rathke's cleft cysts. Acad Radio
4. Bladowska J, Bednarek-Tupikowska G, Biel A, et al. Colloid cyst of the pituitary gland: case report and literature review. Pol J Radiol
5. Cochran EJ. Gattuso P, Reddy VB, David O, Spitz DJ, Haber MH. Central nervous system. Differential Diagnosis in Surgical Pathology
. Philadelphia, PA: Saunders; 2015. 961–1023.
Keywords:© 2017 by Mutaz B. Habal, MD.
Colloid cyst; pituitary colloid cyst; pituitary cysts; sellar cysts