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Case of an asymptomatic pituitary mass
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A 45-year-old Asian woman was referred for the evaluation of a pituitary mass. The patient was well, with no significant past medical history. She complained for 6 months of left lateral tongue pain. A high-resolution MRI scan was ordered to examine the course of the left trigeminal nerve. The trigeminal nerves were normal without enhancement or masses. An incidental finding was reported of a pituitary mass within the right aspect of the pituitary gland.
The patient was referred to the endocrine clinic for evaluation. Her growth and sexual development had been normal. She denied headaches, visual complaints and change in weight or energy. She denied polyuria, polydipsia or nocturia. Her menses were regular and monthly. Her electrolytes and endocrine tests were normal: thyroid-stimulating hormone 1.93 mU/L; free thyroxine index 2.4 ng/dL; prolactin 11.6 ng/mL; somatomedin-C (insulin-like growth factor I) 237 ng/mL; adrenocorticotropic hormone 8 pg/L; cortisol 5.8 mcg/dL (afternoon); luteinizing hormone 10.1 mIU/mL; follicle-stimulating hormone 7.1 mIU/mL. A 0.25-mg IV cosyntropin stimulation test showed normal adrenal function with a basal cortisol of 6.2 mcg/dL (basal) and a 1-hour stimulated cortisol of 25 mcg/dL.
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A dedicated high-resolution MRI of the sella with fine cuts showed a mass that measured 13 mm × 10 mm × 7 mm in transverse, longitudinal and anteroposterior dimensions, respectively, in the right side of the pituitary gland that was hypointense on T1 (Figures 1, 2A) and hyperintense on T2-weighted images (Figure 2B). There was no evidence for enhancement of this lesion after administration of IV contrast gadolinium. The lesion mildly displaced the pituitary stalk to the left, but there was no evidence for mass effect on the optic chiasm or extension into the cavernous sinus. There was no evidence of acute hemorrhage or infarct.
Cystic masses of the sellar region include cystic pituitary adenomas, craniopharyngiomas, Rathke’s cleft cysts, intrasellar arachnoid cysts, epidermoid cysts, dermoid cysts and xanthogranulomas. A solid, cystic mass, especially with calcifications, favors a craniopharyngioma. The absence of a solid component of this patient’s sellar cyst favors either an intrasellar arachnoid cyst or a Rathke’s cleft cyst. An intrasellar arachnoid cyst can be congenital or can be acquired cystic lesions caused by herniation of the arachnoid membrane through an incompetent diaphragma sellae (hole in the dura for the pituitary stalk). Clinical presentation tends to be in adults aged older than 50 years. Rathke’s cleft cysts are benign, non-neoplastic, developmental remnants of the craniopharyngeal duct that are typically located in the sellar and suprasellar region between the anterior and posterior pituitary gland in the region of the vestigial pars intermedia. The pars intermedia is a distinct lobe of the pituitary in lower vertebrates, but in humans, it is atrophic. The peak time of clinical presentation of a Rathke’s cleft cyst is generally the fourth decade.
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Photos courtesy of: Stephanie L.
Lee, MD, PhD |
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Rathke’s cleft cysts are commonly found in up to 22% of autopsies, but they rarely are symptomatic. Symptoms associated with an intrasellar arachnoid cyst or a Rathke’s cleft cyst include headache, endocrine dysfunction and vision loss. Rarely, they can present with chemical meningitis, abscess or intracystic hemorrhage and apoplexy.
The age of the patient and the sellar location of this patient’s cyst are most consistent with a Rathke’s cleft cyst. MRI scans typically will show a well-circumscribed spherical or ovoid lesion of the sellar region (Figures 1 and 2). Most lesions are intrasellar only, but some lesions will extend into the suprasellar cistern (fluid filled space rostral to the pituitary gland). The normal pituitary gland may be displaced in any direction or circumferentially around the cyst (Figure 1). Rathke’s cleft cyst may contain thin, cerebrospinal fluid-like fluid that exhibit a low intensity on T1-weighted images and a high intensity on T2-weighted images; cysts with more proteinaceous, mucoid fluid or hemorrhagic content will have a higher intensity on T1-weighted images. High-signal intensity for cystic fluid on T1-weighted images is caused by protein concentrations of more than 90 g/L and/or the presence of free methemoglobin. Rathke’s cleft cysts do not enhance, but occasionally, there is thin peripheral rim of enhancement that may be caused by inflammation of the cyst wall or the circumferential rim of the displaced pituitary and pituitary stalk, as in our patient (Figures 1B, 1D).
This differentiation of the most common cystic lesions of the sella, craniopharyngiomas, Rathke’s cleft cysts and sellar arachnoid cysts may be difficult to distinguish preoperatively. These cysts should be distinguished before surgery because they are non-neoplastic and may be less aggressively managed compared with neoplastic craniopharyngiomas.
This patient has no symptoms from her Rathke’s cleft cyst. The cyst does not threaten her optic nerve or cavernous sinuses and does not require treatment at this time. A pituitary MRI scan will be repeated in 6 to 12 months and, if unchanged, periodically.
Stephanie L. Lee, MD, PhD, is director of the Thyroid Health Clinic at Boston Medical Center and associate professor of medicine at Boston University School of Medicine. She is also an Endocrine Today Editorial Board member.
Disclosure: Dr. Lee reports no relevant financial disclosures.
For more information:
- Kim JE. J Neurosurg. 2004;100:33-40.
- Shin JL. J Clin Endocrinol Metab. 1999;84:3972-3982.
- Zada G. Neurosurg Focus. 2010;28:1-12.