A rare case of pituicytoma-related hypercortisolism in a patient with Cushing syndrome—case report

Distinguishing between a pituitary adenoma and a pituicytoma can be challenging. Hormonal changes in pituicytomas are uncommon, and the tumor's mass effect has triggered most symptoms. There were only two reported cases of pituicytoma with elevated hormonal levels in patients who presented with Cushing syndrome as of 2017. This report describes a rare case of a patient who had Cushing syndrome from a pituitary-related hypercortisolism, most likely a pituicytoma with neuroendocrine features with the benefit of early detection and surgical resection. Pituicytomas have malignant tendencies while pituitary adenomas are mostly benign, hence the need to distinguish them accurately for prompt treatment and improved prognosis.


Background
Pituicytoma is a low-grade glioma arising from the pituicytes in the neurohypophysis located in the posterior lobe of the pituitary or the pituitary stalk (Chang et al. 2018;Schmalisch et al. 2010). It occurs in adulthood and has a higher male predilection. It can be clinically misdiagnosed as a pituitary adenoma (Chang et al. 2018;Guo et al. 2016). Hormonal changes in pituicytoma are unusual and triggered mainly by the tumor's mass effect. However, there have been recent reports of elevated hormonal levels in such patients initially considered to have a functioning pituitary adenoma (Marco Del Pont et al. 2019). Literature review as of 2019 reported only 6 cases of pituicytoma with elevated hormonal levels in patients who presented with Cushing's disease (Li et al. 2019). The distinction, however, can be challenging. It is unclear whether the pituicytoma has endocrine secretory influence or causes a normal pituitary gland to reach hypersecretory status (Chang et al. 2018;Feng et al. 2018) and hence the focus of this discussion. There is limited literature on pituicytoma-associated hyperactivity of surrounding pituitary glandular tissue, resulting in the clinically abnormal hormone secretion in Cushing syndrome. Pituicytomas have high malignant tendencies, while most pituitary adenomas are benign. Hence the need to increase awareness for prompt management with improved prognosis.
Herein we present a 33-year-old female with multiple possible etiologies of hypertension, diabetes, hypercortisolism, and obesity who was found to have a pituitary mass consistent with a pituicytoma with a good response to treatment.

Case presentation
The patient is a 33-year-old female with a medical history significant for uncontrolled hypertension, diabetes, and hyperlipidemia (diet-controlled and not on medication for preceeding conditions), osteoporosis complicated by a foot fracture after low-intensity trauma, depression, an eating disorder, cocaine abuse, and leukoplakia and papillary hyperplasia of the tongue. Her primary care physician referred her to an endocrinologist for an unrelenting weight gain of 70 pounds in one year. She gained 30 out of the 70 pounds in the month prior to the presentation. She had associated swelling and fat pads in the back of her neck, muscle weakness, joint pain, body aches, hirsutism, and easy bruising. She reported irregular menstrual periods: about 4 to 5 times per year and had never been pregnant (Table 1). She denied the use of exogenous steroids. There was a family history significant for thyroid disease in her mother, coronary artery disease in her father, and a pituitary tumor in her sister. Her examination was pertinent for cushingoid features. Her dexamethasone suppression test indicated early morning cortisol of 17.5 mcg/dL and a serum dexamethasone concentration of 222 ng/dL. Her total 24-h urine cortisol was 336 mcg/24 h. Adrenocorticotropic hormone level was 94 pg/mL, and a chromogranin level was just above the upper limit of normal. All other pituitary hormone levels were within normal limits. Her chest X-ray was negative for any cardiopulmonary pathology. An abdominal computer tomographic scan was negative for an adrenal mass but positive for a 3.2 cm incidental liver lesion, which increased from 1.6 cm on a scan five years prior. She had a repeat dexamethasone suppression test, resulting in a cortisol level of 9.9 mcg/dL and 0.5 mcg/dL of free cortisol. The total early morning cortisol was 11.3 mcg/dL at a dexamethasone level of 461 ng/ dL.
She also had a pituitary protocol contrast magnetic resonance imaging (MRI) that showed a pituitary stalk in the expected location but appeared slightly thickened, with no mass effect, normal cavernous sinus, and a non-enhancing 0.46 × 0.33 cm focus of low signal in the left central portion of the gland on the post-contrast sequences (Figs. 1, 2 and 3). She had a neurosurgical evaluation with transsphenoidal resection of the tumor and biopsy with an inconclusive pathology report (dense collagenous tissue with crush artifact, no evidence of adenoma, and no immunohistochemistry staining for hormones was done). She was started on Mifepristone (a cortisol receptor blocker) at 300 mg daily at incremental dosing and spironolactone at 50 mg twice daily at incremental dosing to 100 mg twice daily with close monitoring of her potassium and blood pressure. The patient had a resolution of symptoms following her medical and surgical management.

Conclusions
It is essential to know the distinction between pituitary adenoma and pituicytoma. The former is a tumor from the cells of the anterior endocrine lobe of the gland with three main pathways of adenohypophyseal cell differentiation for hormone production: corticotrophs, somatotrophs, mammosoamtotrophs, thryotrophs, and gonadotrophs (Cheng et al. 2021b). The World Health Organization requires immunohistochemical staining for hormones produced by these cells in diagnosis (Feng et al. 2018;Gezer et al. 2019). According to the American Cancer Society, about 10,000 pituitary tumors are diagnosed annually in the USA, most of which are benign (Cheng et al. 2021b). A staggering one out of four autopsies will reveal a pituitary tumor in deceased patients who would not have known about the condition (Marco Del Pont et al. 2019;Cheng et al. 2021b). Pituicytomas present as a neoplasm of the sellar and suprasellar regions (World health organization grade 1), which arise from the neurohypophysis or infundibulum of the pituitary and its stalk, as in this case (Marco Del Pont et al. 2019;Li et al. 2019;Gezer et al. 2019;Rumeh et al. 2020). It is a rare tumor that can mimic pituitary adenoma and can be associated with Cushing's disease (Li et al. 2019;Rumeh et al. 2020). Less than 100 cases have been reported thus far, as found through a PubMed literature review. While pituicytomas can cause a range of symptoms, often due to a mass effect, this case highlighted pituicytoma causing Cushing syndrome likely from inducing a hypersecretory effect in the surrounding pituitary gland. This is supported by the absence of evidence of adenoma in pathology. Only few other such cases have been reported in the literature (Schmalisch et al. 2010;Guo et al. 2016;Marco Del Pont et al. 2019;Li et al. 2019;Feng et al. 2018;Gezer et al. 2019;Rumeh et al. 2020;Barresi et al. 2017;Cambiaso et al. 2015;Chakraborti et al. 2013;Yang et al. 2016;Cheng et al. 2021a). In other cases reported in the literature, all adult patients achieved remission of their Cushing disease with surgical dissection of the tumor, as was done for this case.
The patient presented with rapid weight gain concerning hypercortisolism from a paraneoplastic phenomenon. Her weight gain could have been attributed to depression, Cushing's syndrome, or an eating disorder. However, her high levels of the repeated dexamethasone suppression test argued against an unlikely physiological process such as obesity, psychiatric disorders, or bulimia as the etiology of her symptoms. Of note, these conditions can cause an elevated early morning cortisol level which would be suppressible with a higher dexamethasone test. Her free cortisol level of 0.5mcg/dL following a repeat dexamethasone suppression test ruled out an abnormality with cortisol binding.
Findings from her pituitary protocol contrast MRI were consistent with pituicytoma due to the thickening of the pituitary stalk and the particular lesion location in the   One case series noted that the expanded endoscopic transsphenoidal and transplanum was preferred to the craniotomy approach and was associated with higher rates of total gross removal and lower rates of neurological complication, as was observed in our case (Feng et al. 2014). Gross surgical removal should be the intention of management.
In conclusion, pituicytomas are scarce tumors with more malignant tendencies compared to pitutary adenoma and can be associated with cushing syndrome (Feng et al. 2018). Radiological studies are often unable to provide sufficient evidence for the diagnosis of pituicytomas, as they often masquerade as pituitary adenomas. Thus, diagnosing pituicytomas remains a challenge. Surgical resection continues to be the best treatment of pituicytomas to date (Cheng et al. 2021b). Continued evidence and research into this area are needed to diagnose and treat pituicytomas more accurately.

Figures
A non-enhancing 5 mm signal abnormality within the left central portion of the pituitary gland, non-specific, most concerning for a pituitary microadenoma based on the provided clinical history. There is associated mild thickening of the pituitary stalk.