Cushing's Syndrome in a Patient With Rathke's Cleft Cyst and ACTH Cell Hyperplasia Detected by 11C-Methionine PET Imaging-A Case Presentation

Rathke's cleft cysts causing Cushing's disease: Two unique cases and review of the literature

Background

The presentation of isolated Rathke's cleft cysts (RCC) without any associated pituitary adenoma in patients with symptoms consistent with Cushing's disease (CD) remains exceedingly rare. As such, we aim to present two cases of RCC presenting with CD with a resultant resolution of their CD following surgical resection.

Case Description

Here, we present two cases of RCCs presenting with symptoms suggestive of CD. A functional pituitary microadenoma was the presumed diagnosis based on initial clinical presentation and diagnostic imaging suggesting a pituitary lesion. However, pathology results demonstrated no evidence of adenoma but cysts lined with columnar epithelia consistent with RCC. Complete surgical resection was achieved in both patients through endoscopic endonasal pituitary resection with postoperative symptomatic resolution and normalization of cortisol levels. In addition, we discuss the literature on this rare presentation and suggest a pathological mechanism for this unique presentation of RCC-causing CD.

Conclusion

Surgical resection of RCC may provide a "biochemical cure" for patients presenting with CD, as demonstrated by these two unique cases. The clinical features, histological findings, and possible pathological mechanisms for this unique presentation of RCC causing CD discussed lay the groundwork for future studies into the pathophysiology of RCC and CD.

The utility of PET for detecting corticotropinomas in Cushing disease: a scoping review

While magnetic resonance imaging (MRI) is the current standard imaging method for diagnosing and localizing corticotropinomas in Cushing disease, it can fail to detect adenomas in up to 40% of cases. Recently, positron emission tomography (PET) has shown promise as a diagnostic tool to detect pituitary adenomas in Cushing disease. We perform a scoping review to characterize the uses of PET in diagnosing Cushing disease, with a focus on describing the types of PET investigated and defining PET-positive disease. A scoping review was conducted following the PRISMA-ScR guidelines. Thirty-one studies fulfilled our inclusion criteria, consisting of 10 prospective studies, 8 retrospective studies, 11 case reports, and 2 illustrative cases with a total of 262 patients identified. The most commonly utilized PET modalities in prospective/retrospective studies were FDG PET (n = 5), MET PET (n = 5), 68 Ga-DOTATATE PET (n = 2), 13N-ammonia PET (n = 2), and 68 Ga-DOTA-CRH PET (n = 2). MRI positivity ranged from 13 to 100%, while PET positivity ranged from 36 to 100%. In MRI-negative disease, PET positivity ranged from 0 to 100%. Five studies reported the sensitivity and specificity of PET, which ranged from 36 to 100% and 50 to 100%, respectively. PET shows promise in detecting corticotropinomas in Cushing disease, including MRI-negative disease. MET PET has been highly investigated and has demonstrated excellent sensitivity and specificity. However, preliminary studies with FET PET and 68 Ga-DOTA-CRH PET show promise for achieving high sensitivity and specificity and warrant further investigation.

Analysis of the Clinical Characteristics and Pituitary Function of Patients in Central China With Rathke's Cleft Cysts

OBJECTIVE

A Rathke's cleft cyst (RCC) is a common, benign, cystic disease that often leads to hypophyseal dysfunction or head symptoms. The relationship between RCCs and pituitary gland function is not clear. We therefore carried out a study to examine this relationship in greater detail.

METHODS

The study was a retrospective, cohort design in patients diagnosed with a RCC between January 2019 to July 2021 at the First Affiliated Hospital of Zhengzhou University, China.

RESULTS

A total of 221 patients were enrolled and then divided into study cohorts according to the diameter of the RCC, clinical manifestations, and surgical treatment received. The majority of patients were symptomatic (143/221), including 83 cases of dizziness and headache, 9 of vision loss and visual field defect, and 2 of diabetes insipidus. 52 cases had abnormal pituitary function, with 8 cases interestingly showing high adrenocorticotropic-hormone (ACTH) and cortisone levels, while 8 juvenile cases had developed central precocious puberty. Patients with larger RCCs were more likely to present with headaches and dizziness, with subjects who suffered from these symptoms having high ACTH and cortisone levels.

CONCLUSION

Although the size of a RCC is not an important factor influencing hypopituitary function, we consider that endocrine evaluation should be carried out in all patients with a RCC.

New types of localization methods for adrenocorticotropic hormone-dependent Cushing's syndrome

The management of endogenous Cushing's syndrome (CS) typically involves two key steps: (i) confirmation of autonomous hypercortisolism and (ii) localization of the cause to guide treatment. Adrenocorticotropic hormone (ACTH)-dependent CS is most commonly due to a pituitary corticotrope tumor which may be so small as to evade detection on conventional magnetic resonance imaging (MRI). Although biochemical testing (e.g., corticotropin stimulation; dexamethasone suppression) can provide an indication of the likely origin of ACTH excess, bilateral inferior petrosal sinus catheterization offers greater accuracy to distinguish pituitary-driven CS [Cushing's Disease (CD)] from the ectopic ACTH syndrome [EAS, e.g., due to a bronchial or pancreatic neuroendocrine tumor (NET)]. In patients with CD, 40-50% may not have a pituitary adenoma (PA) readily visualized on standard clinical MRI. In these subjects, alternative MR sequences (e.g., dynamic, volumetric, fluid attenuation inversion recovery) and higher magnetic field strength (7T > 3T > 1.5T) may aid tumor localization but carry a risk of identifying coincidental (non-causative) pituitary lesions. Molecular imaging is therefore increasingly being deployed to detect small ACTH-secreting PA, with hybrid imaging [e.g., positron emission tomography (PET) combined with MRI] allowing precise anatomical localization of sites of radiotracer (e.g., ¹¹C-methionine) uptake. Similarly, small ACTH-secreting NETs, missed on initial cross-sectional imaging, may be detected using PET tracers targeting abnormal glucose metabolism (e.g., ¹⁸F-fluorodeoxyglucose), somatostatin receptor (SSTR) expression (e.g., ⁶⁸Ga-DOTATATE), amine precursor (e.g., ¹⁸F-DOPA) or amino acid (e.g., ¹¹C-methionine) uptake. Therefore, modern management of ACTH-dependent CS should ideally be undertaken in specialist centers which have an array of cross-sectional and functional imaging techniques at their disposal.