Changes in hormone production of a recurrent silent corticotroph adenoma of the pituitary: a histologic, immunohistochemical, ultrastructural, and tissue culture study

Phenotype Transformation of PitNETs

Phenotype transformation in pituitary neuroendocrine tumors is a little-known and unpredictable clinical phenomenon. Previous studies have not clearly defined and systematically concluded on the causes of this rare phenomenon. Additionally, the mechanisms of phenotype transformation are not well known. We reviewed cases reported in the literature with the aim of defining phenotype transformation in pituitary neuroendocrine tumors. We present an overview of the wide spectrum of phenotype transformation and its clinical features. We also discuss findings on the potential mechanism of this rare transformation, which may be related to PC1/3, the bioactivity of secretory hormones, gene mutations and the plasticity of pituitary neuroendocrine tumors. Clinicians should be aware of this rare phenomenon and more studies on the underlying mechanisms are required.

Pituitary Adenomas with Changing Phenotype: A Systematic Review

PURPOSE AND METHODS

Phenotype transformation in pituitary adenomas (PA) is a little known and unexpected clinical phenomenon. We describe two illustrative cases and performed a systematic review of cases reported in literature.

RESULTS

Case 1: A 24-year-old woman underwent surgery because of Cushing's disease. A complete tumor resection and hypercortisolism resolution was achieved. Two years later, tumor recurred but clinical and hormonal hypercortisolism were absent. Case 2: A 77-year-old woman underwent surgery due to acromegaly. A complete tumor resection and GH excess remission was achieved. Four years later, tumor recurred but clinical and hormonal acromegaly was ruled out. Search of literature: From 20 patients (including our cases), 75% were female with median age 45 (19) years. Ten patients (50%) had initially functioning PA: 8 switched to NFPA (5 ACTH-secreting PA, 2 prolactinomas and 1 acromegaly) and 2 exchanged to acromegaly from TSH-secreting PA and microprolactinoma. One patient developed a pituitary carcinoma from ACTH-secreting PA. Ten patients (50%) initially had NFPA; 9 developed Cushing's disease (4 silent corticotroph adenomas, 4 null cell PA and 1 managed conservatively). One patient with silent somatotroph PA changed to acromegaly. Treatments before transformation were surgery (80%), radiotherapy (40%), pharmacological (40%) and in 2 patients switching happened without any treatment. Median follow-up until transformation was 72 months (range 12-276).

CONCLUSION

PA can change from functioning to (NF) non-functioning (vice versa) and even exchange their hormonal expression. Clinicians should be aware and a careful lifelong follow-up is mandatory to detect it.

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.

Change in the immunophenotype of a somatotroph adenoma resulting in gigantism

BACKGROUND

Examining the pathologic progression of a pituitary adenoma from the point of a prepubescent child to an adult with gigantism affords us an opportunity to consider why patients may develop secretory or functioning tumors and raises questions about whether therapeutic interventions and surveillance strategies could be made to avoid irreversible phenotypic changes.

CASE DESCRIPTION

A patient underwent a sublabial transsphenoidal resection for a clinically non-functioning macroadenoma in 1999. He underwent radiation treatment and was transiently given growth hormone (GH) supplementation as an adolescent. His growth rapidly traversed several percentiles and he was found to have elevated GH levels. The patient became symptomatic and was taken for a second neurosurgical procedure. Pathology and immunohistochemical staining demonstrated a significantly higher proportion of somatotroph cells and dense granularity; he was diagnosed with a functional somatotroph adenoma.

CONCLUSIONS

While it is likely that the described observations reflect the manifestations of a functional somatotroph adenoma in development, it is possible that pubertal growth, GH supplementation, its removal, or radiation therapy contributed to the described endocrine and pathologic changes.

Silent corticogonadotroph adenomas: clinical and cellular characteristics and long-term outcomes

Silent corticotrophins adenomas (SCAs) are clinically silent and non-secreting but immunostain positively for ACTH. We hypothesize that SCAs comprise both corticotroph and gonadotroph characteristics. Cohort analysis from 1994-2008 with follow-up time ranging from 1-15 years in a tertiary referral center. We compared preoperative and postoperative clinical results and tumor cytogenesis in 25 SCAs and 84 nonfunctioning adenomas in 109 consecutive patients diagnosed pre-operatively with nonfunctioning pituitary adenomas. Clinical outcomes were radiologic and hormonal measures. Pathologic outcomes were expression of relevant pituitary hormones, tissue-specific transcription factors, and electron microscopy features. Preoperative SCA presentation was similar to that observed for nonfunctioning adenomas. However, SCAs recurred postoperatively at a median of 3 years vs. 8 years for nonfunctioning adenomas (p<0.0001). Fifty-four percent of patients with SCAs had new onset postoperative hypopituitarism vs. 17% of nonfunctioning adenomas (p<0.025). SCAs (n=18) were immunopositive for ACTH, cytoplasmic and nuclear SF-1, NeuroD1, DAX-1, and alpha-gonadotropin subunit, but Tpit negative, and co-expression of tumor ACTH with either SF-1 or LH was detected. In contrast, functional corticotroph adenomas (n=11) were immunopositive for ACTH, nuclear SF-1, NeuroD1, and Tpit, but negative for DAX-1, a gonadotroph cell transcription factor. Gonadotroph adenomas (n=23) were immunonegative for ACTH and Tpit but positive for nuclear SF-1, NeuroD1, and DAX-1. SCA electron microscopy demonstrated ultrastructural features consistent with corticotroph and gonadotroph cells. As SCAs exhibit features consistent with both corticotroph and gonadotroph cytologic origin, we propose a pathologic and clinically distinct classification of SCAs as silent corticogonadotroph adenomas.

Secretion of high-molecular-weight adrenocorticotropic hormone from a pituitary adenoma in a patient without Cushing stigmata. Case report

The authors report a case in which a patient harbored a corticotroph macroadenoma that secreted biologically inactive high-molecular-weight adrenocorticotropic hormone (ACTH) as well as authentic ACTH 1-39. The secretion of the high-molecular-weight ACTH was determined using gel chromatography. The authors believe that these two molecules competed with each other at the ACTH receptor and, thus, the bioactivity of ACTH 1-39 was masked and Cushing features were not manifested in the patient. This type of silent corticotroph adenoma may be categorized as a clinically nonfunctioning adenoma. Plasmas from patients with silent corticotroph adenomas, which are identified by positive immunohistochemical staining of ACTH, should be frozen, stored, and analyzed using gel chromatography to examine whether the tumors produce and secrete high-molecular-weight ACTH.

Clinicopathologic study of 123 cases of prolactin-secreting pituitary adenomas with special reference to multihormone production and clonality of the adenomas

BACKGROUND

Prolactinoma is the most invasive type of pituitary adenoma and is generally believed to be well-differentiated adenoma and to produce only prolactin (PRL). The factors related to the various biologic behaviors occurring in patients of different ages and sexes await clarification. Since different immunophenotypes of adenoma may show different biologic behaviors and responses to medical agents, the authors examined hormone production and tried to clarify the clonality of plurihormonal prolactinoma.

METHODS

Clinicopathologic factors were studied in 123 patients with prolactinomas (40 males and 83 females). The specimens were fixed in either 10% neutral buffered formalin or 70% alcohol and used for light microscopy. Alcohol-fixed tissue was used to extract DNA from 26 samples obtained from female patients for human androgen receptor gene (HUMARA) assay.

RESULTS

Sixty one cases (50%) were pure prolactinoma and 62 cases (50%) were plurihormonal prolactinoma. Spearman rank correlation analysis revealed a significant relationship between age and serum PRL level (P = 0.0002), age and tumor volume (P < 0.0001), and tumor volume and serum PRL level (P < 0.0001). Multiple regression analysis showed a significant correlation only between tumor volume and serum PRL level. The Mann-Whitney U test revealed that prolactinomas associated with higher PRL levels, larger adenomas, and higher ages were significantly more invasive to the cavernous sinus and that male patients had significantly higher PRL levels and larger adenomas. The HUMARA assay disclosed that 11 of 13 plurihormonal prolactinomas (85%) were compatible with monoclonal origin.

CONCLUSIONS

The current results suggest that not only can various hormones other than PRL be secreted by prolactinoma, but also that most multihormone-producing prolactinomas are monoclonal in origin.

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.

A case of non-functioning pituitary adenoma with Cushing's syndrome upon recurrence

A 49-year-old woman presented with left visual disturbance. No signs of Cushing's disease were evident. Basal levels of serum cortisol and plasma adrenocorticotropic hormone (ACTH) were 16.8 microg/dL and 66.0 pg/mL, respectively. MRI demonstrated an irregularly shaped large pituitary tumor, and the patient then underwent transsphenoidal surgery. By light microscopy the tumor represented a chromophobic adenoma with a few of the adenoma cells showing immunoreactivity for ACTH. On the basis of clinical and light microscopic examinations, the diagnosis of silent corticotroph adenoma was made. Electron microscopy, however, demonstrated the honeycomb Golgi complex that has been reported as a typical finding of gonadotroph adenomas. MRI taken 7 months after the first operation revealed adenoma regrowth. Transcranial surgery was performed, and histology demonstrated a chromophobic pituitary adenoma with most cells immunopositive for ACTH. She was treated with gamma knife postoperatively. Three months later, MRI revealed remarkable shrinkage of the adenoma, but she developed typical signs and symptoms of Cushing's disease. Thus, the hormone immunostaining and biological activity of pituitary adenomas may change with time.

The multihormonal character of pituitary adenomas: immuno-electron microscopic studies

This study investigates the multihormonal character of pituitary adenomas at the ultrastructural level. The growth hormone (GH)- and prolactin (PRL)-secreting adenomas under study consisted of many moderately or densely granulated cells and a few sparsely or slightly granulated cells. The GH-secreting adenomas showed well-developed cytoplasmic organelles and many large (250 nm or more) or medium-sized (200 nm) secretory granules, as well as a few small (70-150 nm) secretory granules. The PRL-secreting hormones exhibited poorly or slightly developed cyto-plasmic organelles and several small secretory granules. Morphologically and antigenically, these sparsely or slightly granulated cells were similar to those of clinically non-functioning (CN-F) adenomas, which appeared identical to cells expressing little or slight immunoreaction to pituitary hormones at the light microscopic level. As well as those of CN-F adenomas, the small secretory granules of both densely and sparsely granulated cells expressed little or only slight antigenicity of various hormones. Con-comitantly showing slight or moderate antigenicity of hormones biochemically unrelated to GH or PRL, the medium-sized or large secretory granules larger than 140 or 160 nm significantly exhibited intense PRL or GH antigenicity, respectively (Fisher's exact test; P < 0.05 or 0.01). Their GH or PRL antigenicity increased as they grew larger. Showing intermediate cells between sparsely and densely granulated cells, two CN-F adenomas, however, appeared to develop into growth hormone-secreting adenomas. This study led us to conclude that pituitary adenomas may originate from sparsely granulated cells with slight biochemically unrelated hormones, and that their hormonality may be selectively activated singly or multiply in the course of their development.

Silent Corticotroph Adenoma: Case Report and Literature Review

OBJECTIVE

To review the initial clinical manifestations and diagnosis of silent corticotroph adenoma.

METHODS

We report a case and summarize the relevant literature.

RESULTS

A 52-year-old patient with hypopituitarism underwent resection of a silent corticotroph adenoma. A circulating species was detected postoperatively, reactive in a highly sensitive adrenocorticotropic hormone (ACTH) 1-39 immunoradiometric assay (IRMA) and beta-endorphin or beta-lipotropin radioimmunoassay. The basal morning cortisol concentration consistently was <10 microg/dL. Dynamic testing was performed to screen for Addison's disease, congenital adrenal hyperplasia, and Cushing's syndrome. During dexamethasone suppression, the molar concentration of circulating ACTH precursors by a two-site IRMA was 55-fold greater than the concentration of ACTH 1-39 by IRMA. We concluded that the tumor displayed impaired processing of pro-opiomelanocortin (POMC) and secreted a bioinactive POMC-derived peptide that was reactive in the ACTH 1-39 IRMA.

CONCLUSION

Patients with silent corticotroph adenoma do not have clinically evident Cushing's syndrome. In some cases, bioinactive ACTH precursors may be detected by a sensitive ACTH 1-39 IRMA.

Cushing's disease due to female gonadotroph adenoma of the pituitary

A 39-year-old woman presented with amenorrhoea, hyperprolactinaemia and sellar mass. Bromocriptine normalized PRL levels but failed to suppress tumour growth. Subsequently, she developed clinical signs and elevated blood cortisol levels consistent with a diagnosis of Cushing's disease. A pituitary tumour was removed which was immunoreactive for ACTH. Electron microscopic examination, however, revealed a female gonadotroph adenoma indicating that adenoma cells regarded as gonadotrophs by ultrastructural analysis may occasionally secrete ACTH and cause Cushing's disease.

A composite somatotroph-corticotroph pituitary adenoma

A 76-year-old woman presented with enlargement and weakness of her hands and feet coarsening of facial features, proximal muscle weakness, and worsening of her noninsulindependent diabetes mellitus. Serum growth hormone, somatomedin-C, and prolactin levels were elevated. Thyroid function test results and serum cortisol and adrenocorticotropic hormone levels were within normal limits. Luteinizing and follicle-stimulating hormone levels were both low, suggesting possible partial hypopituitarism. Magnetic resonance imaging of the sella demonstrated a pituitary lesion that measured 2.2 x 1 x 0.5 cm; it partially obliterated the suprasellar cistern and it distorted the optic chiasm. Light microscopic and ultrastructural examination of the trans-sphenoidally resected tissues identified characteristic features of 2 discrete pituitary adenomas that were in close apposition, but they were sharply demarcated. The 2 components were a corticotroph adenoma and a sparsely granulated somatotroph adenoma. Multiple adenomas of the pituitary are not rare; however, the majority are endocrinologically "nonfunctional." We report a patient with clinical features of acromegaly whose tumor was a composite lesion: one area exhibited morphological characteristics of a corticotroph adenoma and another distinct area exhibited features of a somatotroph adenoma. The possible histogenesis is discussed.

Changes in the immunophenotype of recurrent pituitary adenomas

Only two cases have been reported of a pituitary adenoma that changed phenotype between its initial resection and recurrence. To determine the frequency of such cases among our patients, we examined the clinical course of these tumors and characterized any patterns. We reviewed the charts of 1023 patients with pituitary adenomas who underwent surgery between 1984 and 1992 at the University of California at San Francisco. Of the 65 patients (6.4%) who had operations for or clinical evidence of tumor recurrence, five (7.7%) had tumors that changed phenotype. The female-to-male ratio was 4:1, and age at the onset of symptoms was 33.2 +/- 15.3 years (mean +/- standard deviation). Changes occurred in hormone production and hormone release after 6.4 +/- 3.4 years. At some point, all five tumors were invasive and four were macroadenomas. Two patients had more than one operation for tumor recurrence; three had silent or symptomatic pituitary apoplexy; and three had undergone sellar irradiation before the changes in phenotype occurred. The behavior of these tumors therefore seems to be aggressive. We do not yet know whether phenotypic changes in pituitary adenomas have any treatment implications. Therefore, we advocate the complete immunostaining of primary and recurrent pituitary adenomas so that additional data about their clinical course can be collected.

Thyrotropin-producing pituitary adenomas

To evaluate the biology of thyrotropin (TSH)-producing pituitary adenomas, the authors reviewed the charts of 19 patients who underwent transsphenoidal surgery within a 15-year period at the University of California, San Francisco (UCSF). Between 1989 and 1991, the period during which immunostaining techniques were used consistently for diagnosis, 2.8% of the pituitary adenomas treated at UCSF were TSH-producing. The rate of reoperation for tumor recurrence was 10.5%. Before pituitary surgery, more than one-third of the 19 patients had undergone thyroid ablation. Two patients had a history of Hashimoto's thyroiditis. The female:male ratio was 1.7:1. Women tended to develop these tumors at a younger age and had a longer history of symptoms but their tumors were smaller and less often invasive than those seen in men. About 50% of the tumors were purely TSH-producing and 50% were plurihormonal, including five that produced both TSH and adrenocorticotroph hormone. All tumors were macroadenomas. Before surgery, 46% of the patients had abnormal electrocardiographic findings; 16% had a rapid onset of severe neurological conditions either before or after surgery. It is concluded that TSH-producing adenomas are more common in patients who undergo surgical treatment than was previously thought. In addition, they occur more frequently in women, have a different biology in women than in men, and tend to be associated with potentially life-threatening cardiovascular and neurological complications.

Silent corticotroph adenoma with multiple cysts: Pars intermedia tumor?

A silent corticotroph adenoma with multiple cysts was found incidentally at autopsy. By immunohistochemistry, most of the adenoma cells contained reactivity for adrenocorticotropic hormone and beta-endorphin; a few cells stained for beta-subunit of luteinizing hormone. The cysts, interspersed within the tumor, were lined by cuboidal epithelium with foci of stratified squamous epithelium. The lining cells contained immunoreactive keratin; some cells were positive for S-100 protein or glial fibrillary acidic protein, and a few cells were also immuno-stained for adrenocorticotropic hormone and beta-endorphin. It is suggested that this tumor may represent a neoplasm of pars intermedia derivation.