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

Abstract

Background: Adrenocorticotropic Hormone (ACTH)-dependent Cushing's Syndrome (CS) is most often caused by a pituitary adenoma. Although rarely, it can also result from pituitary corticotroph cell hyperplasia (CH). Reports on concomitant pituitary lesions including ACTH-producing adenomas and Rathke's cleft cysts (RCCs) have been published. Positron emission tomography (PET), using 11 C-labelled-methionine (MET) as a tracer and co-registered with magnetic resonance imaging (MRI) has been shown to be useful in the diagnosis of pituitary collision lesions, however, its role is still under investigation. In this work we present the case of a patient in whom CS was caused by non-adenomatous CH within the wall of an RCC. Case Summary: In 2015 a patient with signs and symptoms of CS was referred to our Department. Biochemical studies repeatedly showed elevated midnight serum cortisol and ACTH levels. Magnetic resonance imaging of the sellar region revealed an RCC and MET-PET/MR showed heterogeneous labelled-methionine metabolism in the vicinity of the cyst's wall. Transsphenoidal surgery resulted in rapid, complete and lasting relief of symptoms. Histopathological examination demonstrated an RCC and CH. Conclusions: Concomitance of pituitary focal lesions is a rare phenomenon. Methionine-labelled PET/MR may be useful in the diagnosis of collision sellar lesions, including CH. Corticotroph cell hyperplasia can present as mild and fluctuating hypercortisolaemia.

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

“…In the literature, to date, there are several reported cases of pituitary adenoma and hyperplasia presenting in association with RCC. [ 2 , 17 , 21 ] These typically present as nonfunctional pituitary adenomas and prolactinomas coexisting with RCC in patients presenting with endocrinological imbalances and compressive effects, which resolved after transsphenoidal resection. [ 21 ] Even more rare is the presentation of RCC causing similar endocrinological symptomology without evidence of concurrent pituitary adenoma on histology.…”

“…[ 2 ] In one case of CD in a female patient in her 3 rd decade, corticotroph cell hyperplasia/ ACTH-positive cells penetrating the wall of the RCC were seen on histology. [ 17 ] Findings demonstrated an RCC, numerous ACTH+ cells, and, to a lesser extent, thyroid-stimulating hormone (TSH)+ cells. [ 17 ] In our patients, biopsy demonstrated unremarkable pituitary tissue with adjacent islands of eosinophilic acellular material and strips of ciliated epithelium, a colloid nodule, and a fibrous membrane/wall.…”

“…[ 17 ] Findings demonstrated an RCC, numerous ACTH+ cells, and, to a lesser extent, thyroid-stimulating hormone (TSH)+ cells. [ 17 ] In our patients, biopsy demonstrated unremarkable pituitary tissue with adjacent islands of eosinophilic acellular material and strips of ciliated epithelium, a colloid nodule, and a fibrous membrane/wall. Biopsy findings in our second patient described Crooke’s hyaline changes.…”

“…[ 13 ] However, minimal data exist discussing isolated RCCs without any associated pituitary adenoma causing CD. [ 17 ] Here, we present two cases of RCCs presenting symptoms suggestive of CD. We discuss the clinical features and histological findings and suggest a pathological mechanism for this unique presentation of RCC-causing CD.…”