Endocrine Abstracts

Introduction: Dermoid cysts are rare (0.5% of intracranial tumours). They are best considered a spectrum: from epidermoid cysts containing desquamated squamous epithelium to teratomas containing all three embryonic tissues. Sellar dermoid cysts are even rarer [Orpha.net ID: ORPHA:91351].

Case: A 47-year old white British male was referred following incidental discovery of bitemporal field defect on routine eye test. He was otherwise completely asymptomatic. A 27mm x 24 mm x 27 mm intra-/suprasellar lesion was found on orbital MRI. A pituitary MRI with contrast showed the same mass with a small left lateral extension, superomedial to the proximal middle cerebral artery. The tumour was heterogeneous with areas of high T1 and T2 signal. The bulk of the tumour showed low signal on the fat-suppressed sequences. The suprasellar component displaced the optic chiasm and stretched the pre-chiasmatic segments. The pituitary gland was separate from the tumour. Numerous T1 hyperintense foci were found in the third and left lateral ventricles and in subarachnoid spaces overlying the frontal lobes and the cerebellar hemisphere. The radiological diagnosis was either a craniopharyngioma or a dermoid cyst that has ruptured with intracranial dissemination. Baseline pituitary function was normal: cortisol 477nM/l, testosterone 12 nmol/l, FSH 4.1 IU/l, LH 2.8 IU/l, IGF-1 16.8 nmol/l (ref 7-28), free T4 12 pmol/l, TSH 4.2 mU/l, prolactin 270 mU/l. OCT-RNFL analysis showed deteriorating fibre loss and thinning. Endoscopic transsphenoidal debulking was done. Histology showed keratinous material with a basket weave appearance. Cam5.2 stain showed <20 cells. Reticulin staining and immunohistochemistry for synaptophysin, p53, Ki-67, pituitary hormones and transcription factors were negative. Visual fields improved. Postoperative endocrine function showed suboptimal cortisol (402 nmol/l) and GH (2.0) on insulin tolerance test. A 3-month postoperative scan showed extensive debulking with a 11 mm residuum. Optic chiasm was decompressed. The patient further scans at 6 monthly intervals. The first showed no change. The second showed increase in the residuum with no immediate pressure on the chiasm. Further proactive surgery is being offered to patient.

Discussion points: • This was an unusual presentation of a very rare condition. Despite rupture of the cyst, the patient was asymptomatic and the field defect was an incidental finding.

• The pituitary function was preserved at presentation despite a large tumour, possibly indicating slow growth over time.

• Histologically, the lesion was closer to the epidermoid end of the spectrum but it is difficult to prognosticate regrowth. Close monitoring is advisable.