THU104 An Atypical Case Of A Suprasellar Cyst: A Diagnostic Challenge

Disclosure: A. Chen: None. S. Zachariah: None. B. Wong: None. E. Owusu: None. A. Levitt: None. R. Todor: None. P. Kishore: None. Background: Cystic sellar masses may be challenging to diagnose on a clinical, imaging, and histopathological basis due to overlapping features. We report a case of a cystic sellar mass in which traditional imaging findings did not correspond to its histopathological findings. Clinical Case: A 37-year-old female presented with headaches and bilateral blurry vision for two months with acute worsening of left peripheral vision for one week. She denied irregular periods, hirsutism, or breast discharge. Ophthalmology evaluation found left temporal field vision loss but normal maculae/optic nerves. MRI pituitary exhibited 2.3 x 1.5 x 1.7 cm complex cystic suprasellar mass with partial rim enhancement, thought to represent a cystic macroadenoma. Initial tests were notable for negative HCG, prolactin 96.32 mIU/mL (n < 23.3 mIU/mL), TSH 9.440 uIU/mL (0.270-4.2 uIU/mL), normalized to 0.855 uIU/mL on repeat testing, FT4 0.748 ng/dL (n = 0.75 – 2.0 ng/dL). IGF-1, ACTH, AM cortisol, FSH, and LH were within normal limits. She was started on cabergoline prior to trans-nasal-sphenoid resection with cyst drainage of white and thick content. Histopathology exhibited a squamous epithelium-lined cyst with no columnar epithelium or mucin-containing cells, consistent with an epidermoid cyst (EC), although the differential included a Rathke’s cleft cyst (RCC). No pituitary tumor was noted. A re-evaluation of MRI in multidisciplinary rounds deemed epidermoid cyst unlikely, given that these present with restricted diffusion. Our patient had overall T2 hyperintensity with an associated T2 hypointense nodule and did not restrict diffusion [1]. After interdisciplinary discussion, including imaging and pathology review, it was felt that the most likely diagnosis was RCC with squamous metaplasia. After surgery, the patient's symptoms and visual function completely recovered, and follow-up imaging is scheduled. Conclusion: Differentiating RCC with squamous metaplasia from EC can be challenging since both may present with a squamous epithelial lining [2]. Rates of progression and recurrence vary amongst cysts; therefore, making an accurate diagnosis is essential for selecting management, predicting the likelihood of recurrence, and guiding postoperative surveillance. This case is unique in that radiologic features were more helpful than histopathology in determining the diagnosis and highlights the importance of collectively considering clinical, imaging, and histopathological features in making a final diagnosis. References: 1. Wilms, G., MRI of the pituitary gland, by Jean-François Bonneville, Fabrice Bonneville, Françoise Cattin, Sonia Nagi. Neuroradiology, 2016. 58(12): p. 1241-1242. 2. Zada, G., et al., Craniopharyngioma and other cystic epithelial lesions of the sellar region: a review of clinical, imaging, and histopathological relationships. Neurosurg Focus, 2010. 28(4): p. E4. Presentation: Thursday, June 15, 2023