Silent Corticotroph Adenoma: Case Report and Literature Review

Identifying Glucocorticoid Insufficiency in Silent Corticotroph Adenoma with Elevated Adrenocorticotropic Hormone

Silent corticotroph adenoma (SCA) is as an aggressive pituitary tumor. A 48 year old man developed hypogonadotrophic hypogonadism. The basal morning adrenocorticotropic hormone (ACTH) was elevated, but the basal morning and peak after ACTH (1-24) stimulation cortisol were normal. A 3.7 cm sellar mass with evidence of internal hemorrhage, encasement of the right internal carotid artery, and invasion of the right cavernous sinus were identified, resected, and stained positive for ACTH. Over the next 5 years, the basal morning ACTH and cortisol were normal, and imaging revealed the presence of a small residual tumor. One year later, the patient became fatigued and nauseated, with elevated ACTH. An overnight metyrapone stimulation test (OMST) revealed glucocorticoid insufficiency, without further increase in ACTH. Symptoms resolved with hydrocortisone treatment. This case study suggests that SCA can secrete an ACTH precursor that is detected by clinical assays but is not active biologically. Postoperative OMST reveals glucocorticoid insufficiency in this context.

Predictors of silent corticotroph adenoma recurrence; a large retrospective single center study and systematic literature review

PURPOSE

Silent corticotroph adenomas (SCAs) are clinically silent and non-secreting, but exhibit positive adrenocorticotropic hormone (ACTH) immunostaining. We characterized a single center cohort of SCA patients, compared the SCAs to silent gonadotroph adenomas (SGAs), identified predictors of recurrence, and reviewed and compared the cohort to previously published SCAs cases.

METHODS

Retrospective review of SCA and SGA surgically resected patients over 10 years and 6 years, respectively. Definitions; SCA-no clinical or biochemical evidence of Cushing's syndrome and ACTH positive immunostaining, and SGA-steroidogenic factor (SF-1) positive immunostaining. A systematic literature search was undertaken using Pubmed and Scopus.

RESULTS

Review revealed 814 pituitary surgeries, 39 (4.8%) were SCAs. Mean follow-up was 6.4 years (range 0.5-23.8 years). Pre-operative magnetic resonance imaging demonstrated sphenoid and/or cavernous sinus invasion in 44%, 33% were > 50% cystic, and 28% had high ACTH levels pre-operatively. Compared to SGAs (n = 70), SCAs were of similar size and invasiveness (2.5 vs. 2.9 cm, p = 0.2; 44 vs. 41%, p = 0.8, respectively), but recurrence rate was higher (36 vs. 10%, p = 0.001) and more patients received radiation therapy (18 vs. 3%, p = 0.006). Less cystic tumors (0 vs. 50%, p < 0.001) and higher pre-operative ACTH levels (54 vs. 28 pg/ml, p = 0.04) were predictors of recurrence for SCAs.

CONCLUSION

This review is unique; a strict definition of SCA was used, and single center SCAs were compared with SGAs and with SCAs literature reviewed cases. We show that SCAs are aggressive and identify predictors of recurrence. Accurate initial diagnosis, close imaging and biochemical follow up are warranted.

Expression of adrenocorticotropic hormone, prolactin and transcriptional factors in clinically nonfunctioning pituitary adenoma

We describe here a case of a clinically nonfunctioning pituitary adenoma, but with expression of ACTH and PRL. A 42-year-old woman was referred to our department for further evaluation of pituitary tumor. She had no acromegaloid features, and no typical Cushingoid features. She had no galactorrhea, and had regular menses. GH, IGF-I, LH, FSH, TSH, ACTH and cortisol levels in blood were all within the normal ranges, while PRL levels were mildly elevated. Both ACTH and cortisol levels were adequately increased in response to CRH, and both were suppressed by a small dose of dexamethasone. Plasma ACTH and cortisol levels were decreased at night, suggesting the circadian rhythms for plasma ACTH levels were undisturbed. Based on these findings we did not clinically suspect ACTH-producing tumor, however immunohistochemistry revealed ACTH immunoreactivity in the pituitary adenoma. Therefore, the tumor was considered a silent corticotroph adenoma. PRL was co-expressed in a significant subpopulation of ACTH-immunoreactive tumor cells. Ptx1, Neuro D1, and T pit were densely expressed and Pit-1 was sparsely expressed in the nuclei of adenoma cells. It is therefore possible that a tumor originating in an immature or uncommited adenohypophysial stem cell may later differentiate into different cell types due to a combination of certain specific transcriptional factors.

Silent corticotroph adenomas

Silent corticotroph pituitary adenomas (SCA) are defined as pituitary adenomas showing positive staining for adrenocorticotrophic hormone in immunohistochemical studies, but not associated with perioperative clinical or laboratory features of hypercortisolaemia. They account for 1.1-6% of surgically removed pituitary adenomas. Currently, two distinct pathologic subtypes of SCA are recognised. Their pathogenesis remains unclear. They present with local mass effects (headache, visual deterioration, cranial nerve palsies, endocrine dysfunction). The lack of manifestations of cortisol excess has not been conclusively explained. In surgical series, most tumours are macroadenomas with suprasellar extension present in 87-100% of the cases; this is in contrast to Cushing's disease, which is mostly attributed to microadenomas. Surgery remains the main therapeutic approach. Attempts to identify predictors of recurrence have not been successful. Management and follow-up protocols should be planned taking into account their potential aggressive behaviour, particularly upon recurrence. The development of florid pituitary Cushing's syndrome and local recurrence followed by metastatic disease (occasionally outside the central nervous system) have been rarely reported.

Silent corticotroph adenomas: further clinical and pathological observations

Adrenocorticotroph cell pituitary adenomas immunoreactive for adrenocorticotropic hormone (ACTH) but unassociated with preoperative signs of hypercortisolism constitute between 6% and 43% of all ACTH adenomas. Few large series have been published. At our referral center for pituitary diseases, we have encountered 12 patients with silent ACTH adenomas, none of whom exhibited definite clinical features of hypercortisolism preoperatively. Two patients presented with apoplexy, and in 2 patients preoperative neuroimaging studies mimicked craniopharyngioma. Pathological examination revealed 8 adenomas with variably basophilic cytoplasm (type I, including 1 each with coarse basophilic granules and Crooke's hyaline change) and 4 with predominantly chromophobic cytoplasm (type II). Diffuse versus patchy (30% to 50% of cells) immunostaining best distinguished these 2 types; calcitonin staining was focal or negative in both. Two patients had unexpected postoperative courses consistent with acute cortisol insufficiency; 1 patient suffered from a severe flu-like illness, and the other had dizziness and was found to have a serum cortisol level of < 1.0 microg/dL. Both patients improved after cortisol replacement followed by a slow taper. Another patient developed 2 separate pituitary adenomas, a silent ACTH adenoma followed by a pure prolactinoma resected months later. Clonality studies demonstrated that the 2 tumors had arisen from different clonal populations. These cases offer additional insights into clinical, neuroimaging, histological, and biological features of silent ACTH adenomas. Because 2 of these patients seemed to require postoperative cortisol supplementation that otherwise would not have been given, clinicians should be notified about ACTH immunostaining in adenomas from patients without preoperative diagnoses of Cushing's disease, to optimize postoperative care.

Clinical Characteristics of Silent Corticotrophic Adenomas and Creation of an Internet-accessible Database to Facilitate Their Multi-institutional Study

OBJECTIVE

Silent corticotrophic adenomas (SCAs) of the pituitary gland present as clinically nonfunctioning sellar lesions, with normal serum and urine hormone testing results, but stain positively for adrenocorticotropic hormone in immunohistochemical analyses. These tumors are now more readily recognized, but determination of their natural history and responses to treatment is difficult because of their rarity. We report the diagnoses and outcomes for a series of patients with SCAs, and we describe the creation of an Internet-accessible database (www.hsc.virginia.edu/neuro/neurosurgery/pituitary.html) for collection of multi-institutional data on these lesions.

METHODS

The medical records of patients with documented SCAs who were treated at the University of Virginia between 1991 and 2002 were reviewed. A comprehensive data collection form was then created and posted online.

RESULTS

Twenty-seven patients with SCAs were identified, with a female predominance (70%, P = 0.04). Headache was the most common presenting symptom (70%), followed by visual field deficits (52%), acute or subacute pituitary apoplexy (33%), cavernous sinus syndrome (18.5%), and hypopituitarism (11.1%). Extrasellar extension was noted for 92.6% of patients on preoperative magnetic resonance imaging scans. Transsphenoidal surgery was performed for all patients. Follow-up information was available for all patients (median, 60 mo; range, 3–254 mo). Postoperatively, 33% of patients received radiotherapy. Recurrence was noted for 37% of all patients and 41.7% of patients who did not receive postoperative radiotherapy.

CONCLUSION

SCAs, although clinically nonfunctioning, may behave like aggressive adrenocorticotropic hormone-secreting adenomas and therefore should receive vigorous follow-up monitoring, with consideration being given to the recommendation of radiotherapy in cases with residual tumor.

Comparison of ACTH secretion in Cushing's adenoma and clinically silent corticotroph adenoma by cell immunoblot assay

Immunocytochemical staining and cell immunoblot assay (CIBA) were performed in adenoma tissue from five patients with Cushing's disease and three patients with clinically silent corticotroph adenomas. All five patients with Cushing's disease showed hypersecretion of ACTH (130, 190, 331, 120, and 130 pg/ml), high levels of serum cortisol (26.6-44.0 micrograms/dl), and symptoms of Cushing's disease. All three patients with silent corticotroph adenoma showed hypersecretion of ACTH (110, 140, and 160 pg/ml) and normal levels of serum cortisol (11.4-26.8 micrograms/dl). The size of the pituitary adenoma on magnetic resonance imaging was smaller in patients with Cushing's disease (mean 8.2 mm) than in patients with silent corticotroph adenoma (mean 26.7 mm) (p = 0.001). Transsphenoidal surgery was performed to totally resect the adenoma tissue. Immunostaining for ACTH showed diffuse ACTH-immunopositive cells in all eight adenomas. CIBA technique showed a good correlation between percentage of ACTH-immunopositive cells and level of plasma ACTH in patients with Cushing's disease but no correlation between the two parameters in patients with silent corticotroph adenoma. The percentage of ACTH-secreting cells and the amount of hormone secreted by a single cell are too low in silent corticotroph adenomas to cause an increase in plasma ACTH level corresponding to the large tumor size.

Clinically silent corticotroph tumors of the pituitary gland

OBJECTIVE

To determine the clinical presentation, imaging characteristics, microscopic and ultrastructural characteristics, and treatment outcomes of patients with clinically silent pituitary corticotroph adenomas.

METHODS

All silent corticotroph adenomas diagnosed at the Mayo Clinic during the years 1975 through 1997 were selected from the files of the Mayo Tissue Registry.

RESULTS

We studied 23 cases, occurring in 16 male and 7 female patients (age range, 11-79 yr; mean age, 48 yr), who presented with headaches (50%), visual field defects (61%), extraocular muscle paresis (13%), hypopituitarism (26%), and galactorrhea/amenorrhea (43%/29% of the female patients). No patients exhibited clinical hypercortisolism. All tumors were macroadenomas (2.4+/-0.8 cm; range, 1.5-4.0 cm) and exhibited suprasellar extension in 87% of the cases and hemorrhage, necrosis, and/or cystic changes in 61%. All tumors stained were variably periodic acid-Schiff-, adrenocorticotropic hormone-, and beta-endorphin-positive, particularly Subtype I lesions. Ultrastructural classification was performed in 19 cases. In a comparison of Subtype I and II tumors, differences were observed with respect to sex (male/female, 1.4:1 versus 6:1), preoperative hyperprolactinemia (5 of 16 versus 0 of 6 cases), preoperative hypopituitarism (9 of 16 versus 5 of 7 cases), radiographic or gross invasion (7 of 16 versus 5 of 7 cases), and partial or total postoperative pituitary failure (6 of 16 versus 6 of 6 cases). The overall median postoperative follow-up period was 4.9 years (range, 0.3-16.6 yr); 54% of the patients had persistent or recurrent tumors.

CONCLUSION

Clinically silent corticotroph adenomas behave in an aggressive manner and are characterized by the following: lack of clinical signs or symptoms of Cushing's syndrome and normal cortisol levels; no or only minor elevations of serum adrenocorticotropic hormone levels; macroadenomas with hemorrhagic infarction; and presentation dominated by mass effect symptoms. The high persistence/recurrence rate underscores the need for long-term follow-up.