MGMT Immunoexpression in Silent Subtype 3 Pituitary Adenomas: Possible Therapeutic Implications

The objective of the study was to assess O ⁶-methylguanine-DNA methyltransferase (MGMT) immunoreactivity in pituitary adenomas of silent subtype 3 as a potential indicator of temozolomide susceptibility. The Mayo Clinic Anatomic Pathology Database was searched for all cases of silent subtype 3 pituitary adenoma. Each of the 23 cases identified had been confirmed on the basis of histology, immunohistochemical staining for pituitary hormones, as well as on diagnostic ultrastructural criteria. Unstained microscopic sections were immunostained for MGMT and were semiquantitatively assessed. Of the 23 tumors examined, 18 (78%) showed no MGMT immunoreactivity. The remaining five (22%) showed immunoreactivity in ≤50% of tumor cells. Among eight of the most clinically aggressive tumors in this study, six (75%) lacked MGMT immunoreactivity. The observed lack of or low-level expression of MGMT by this distinctive, clinically aggressive form of pituitary adenoma suggests potential efficacy of treatment with the alkylating agent temozolomide.     

Combined sellar fibrosarcoma and prolactinoma with neuronal metaplasia: Report of a case unassociated with radiotherapy

We report the occurrence of a primary pituitary fibrosarcoma causally unrelated to radiotherapy, admixed in association with a prolactin cell pituitary adenoma showing neuronal metaplasia. These unique findings were associated with multiple endocrine neoplasia type 1 (MEN 1). Primary fibrosarcoma involving the sella is a very rare tumor. The majority of cases have been associated with prior irradiation of either a pituitary adenoma or a craniopharyngioma. Pituitary adenoma with neuronal metaplasia is also rare and usually occurs in the setting of acromegaly. Despite the intimate association of both elements in our lesion, no transition of adenoma to sarcoma was demonstrable by immunohistochemistry or in situ hybridization studies.     

Endocrine surgical pathology: lesson from pituitary cases that are discordant between clinical and pathologic diagnoses

There are a variety of clinicopathologic situations of pituitary lesions that could cause a discordance of diagnosis between clinicians and pathologists. This may be caused by confusion of terminology such as “nonfunctioning adenoma” and “null cell adenoma.” “Clinically nonfunctioning pituitary adenomas” comprise several pathologically different types of tumors that belong to one of three major cell lineages of adenohypophysial cell types. “Null cell adenoma” was originally defined by ultrastructural features but recently refers to immunonegative adenomas. Unique and unusual types of adenomas such as adenomas with “honeycomb Golgi” appearance and silent subtype 3 adenomas may cause a discordance of diagnosis. Because of mild elevation of prolactin levels, these adenomas are sometimes erroneously diagnosed as prolactinoma. Careful pathologic study with immunohistochemistry and electron microscopic examination, as well as communication between clinicians and pathologists, is vital. Confusion of terminology should be discussed. Awareness of rare disease entities is also required. Thorough analysis of individual cases with diagnostic inconsistency may provide a useful lesson for better understanding of endocrine diseases and for appropriate treatments.     

Monomorphous Plurihormonal Pituitary Adenoma of Pit-1 Lineage in a Giant Adolescent with Central Hyperthyroidism

Thyrotropin (TSH)-secreting pituitary adenomas are exceedingly rare at the pediatric age and no cases of co-secretion with other pituitary hormones in these tumors have been described in this age range. We present a case of a monomorphous plurihormonal pituitary adenoma that co-secreted TSH and GH in a pediatric patient. A 13-year-old male presented with increasing height velocity (17.75 cm/year, 9.55SD), weight loss, and visual impairment. Initial biochemical evaluations revealed secondary hyperthyroidism. A giant pituitary tumor compressing the surrounding structures was detected by magnetic resonance, and a transsphenoidal surgery was initially performed. Pathological examinations revealed an atypical, monomorphous plurihormonal Pit-1 lineage tumor with mixed features of silent subtype 3 adenoma and acidophil stem cell adenoma. In the postoperative period, secondary hyperthyroidism recurred with high levels of both GH and IGF1. In addition, due to tumor re-growth, a multimodality treatment plan was undertaken including surgery, somatostatin analogs, and radiotherapy. We report the first pediatric case of a plurihormonal TSH- and GH-secreting pituitary adenoma, further expanding the clinical manifestations of pediatric pituitary tumors. Comprehensive pathological evaluation and close follow-up surveillance are crucial to the prompt delivery of the best therapeutic options in the context of this particularly aggressive pituitary tumor.     

Silent mixed growth hormone cell-prolactin cell pituitary adenoma

The case of a 51 -year-old man with recurrent nonfunctioning pituitary adenoma is presented. Despite clinically and endocrinologically normal pituitary function in regard to growth hormone and prolactin, many growth hormone- and prolactin-positive cells were immunohis-tochemically detected in adenoma tissue. Furthermore, a quite rare tumor of silent mixed growth hormone cell-prolactin cell pituitary adenoma was confirmed by the double-labeling immunoelectron-microscopical study.     

Heterogeneity of secretory granules of silent pituitary adenomas

Silent pituitary adenomas were compared with hormonally active tumors taking into account the size, number, and ultrastructural characteristics of secretory granules (SG). The study group (a total of 79 primary pituitary adenomas) comprised 27 silent, 21 growth hormone (GH)-producing-, 16 prolactin (PRL)-producing-, 5 GH-PRL-producing- and 10 adrenocorticotropic hormone (ACTH)-producing adenomas. The SG of silent adenomas were significantly smaller than SG in endocrine active adenomas. All hormonally inactive tumors also contained small (mean, 94 nm) specific cytoplasmic granules, designated "silent adenoma granules" (SIG). The fine structural features of the SIG included: a flocculent, granular material occupying an eccentric position in a larger vesicle limited by a double membrane. In the silent adenomas this particular granule was present in up to 90% of the adenoma cells and constituted approximately 10 to 50% of the granules in each cell. These granules were not seen in hormonally active tumors and considered therefore diagnostic of silent pituitary adenomas.     

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

A 19-year-old man with blurred vision, headache, and no signs or symptoms of hormone excess was found to have a pituitary adenoma. The tumor was removed by a transfrontal approach. He had postoperative radiation therapy, but subsequently had three recurrences, all removed surgically. By histology, the tumor was a chromophobic, slightly acidophilic pituitary adenoma. Immunohistochemistry revealed the presence of adrenocorticotropin (ACTH) in all four biopsies, alpha-subunit of glycoprotein hormones, and, to a lesser extent, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the third and fourth tumor resection specimens. Ultrastructurally, the tumor had typical features of a silent corticotroph adenoma subtype 2. In tissue culture, the second, third, and fourth specimens released ACTH, alpha-subunit, FSH, and LH and responded to corticotropin-releasing hormone with increased release of ACTH, alpha-subunit, FSH, and LH. To our knowledge only one silent corticotroph adenoma has been reported previously which expressed plurihormonality. Change in immunohistochemical profile in malignant tumors is a well-known phenomenon; however, it was not reported previously in benign pituitary adenomas. The factors accounting for changing tumor phenotype are unknown.     

Pituitary Adenoma with Tumoral Granulomatous Reaction

Herein, we report a unique case of an adult male with a corticotrophic pituitary adenoma of silent subtype 1 exhibiting conspicuous idiopathic tumoral noncaseating granulomatous inflammation. The lesion was unassociated with clinical or laboratory evidence of either systemic sarcoidosis or infection. Histochemical and polymerase chain reaction (PCR) studies revealed neither fungi nor tubercle bacilli. We suggest that tumoral production of an as yet uncharacterized antigen may have induced the granulomatous inflammatory reaction.     

Vascular Endothelial Growth Factor (VEGF) Expression in Human Pituitary Adenomas and Carcinomas

Vascular endothelial growth factor (VEGF) is a key mediator of endothelial cell proliferation, angiogenesis, and vascular permeability. Little is known about its expression in human pituitary adenomas. We examined 148 human pituitary adenomas for VEGF protein expression by immunohistochemistry. The strongest immunoreactivity was present in GH adenomas, corticotroph, silent corticotroph, silent subtype 3, and nononcocytic null cell adenomas. GH adenomas treated with octreotide strained less intensely than did untreated tumors. Relatively weak staining was present in PRL, gonadotroph, thyrotroph, and oncocytic null cell adenomas in the same sections showed evidence of down-regulation of VEGF protein expression in adenomas. Pituitary carcinomas usually had stronger staining than adenomas. In situ hybridization studies with oligonucleotide probes showed positive staining in all groups with stronger staining in GH, ACTH, TSH, and gonadotroph adenomas and in pituitary carcinomas. These results indicate that VEGF expression is more prominent in certain adenoma subtypes, that decreased expression occurs in adenomas as compared to nontumorous pituitary and that carcinomas show increased VEGF expression relative to adenomas suggesting up-regulation of VEGF during pituitary tumor progression.     

Pituitary adenoma with rich folliculo-stellate cells and mucin-producing epithelia arising in a 2-year-old girl

Pituitary adenoma is a rare neoplasm in childhood, with prolactin and adrenocorticotropic hormone (ACTH)-secreting adenomas predominating in this age group. Herein is reported a case of an ACTH-producing macroadenoma with an unusual histology that occurred in a 2-year-old girl. Because of the patient's age and the macroadenoma's suprasellar location and large size (up to 4 cm in diameter), radical surgery was performed under the suspicion of craniopharyngioma or germ-cell tumor. Pathologically, it was a unique pituitary adenoma composed of monotonous ACTH-producing cells, smaller folliculo-stellate cells (FSC), and mucin-producing cells. The FSC, non-hormone-secreting pituitary cells of uncertain function, were confirmed by their S-100 protein, glial fibrillary acidic protein and cytokeratin expression immunoprofiles. The abrupt transition between the prominent gland-forming mucin-producing epithelia and the FSC component suggested that the mucin-producing epithelia might be derived from the FSC. This association might represent so-called 'retrodifferentiation' of adenoma cells to the FSC and the precursor cells of Rathke's pouch.     

A Silent Follicle-Stimulating Hormone-Producing Pituitary Adenoma in a Teenage Male

An 18-year-old male was referred to Toranomon Hospital seeking reoperation for recurrent clinically nonfunctioning pituitary adenoma. A pituitary macroadenoma was first suspected at age 15 due to intractable headaches. Endocrine data were unremarkable except slightly elevated serum follicle-stimulating hormone (FSH). Transsphenoidal surgery done at another hospital achieved partial tumor removal but the remaining tumor regrew 2 years after surgery. The recurrent tumor was completely and selectively removed on repeat surgery at Toranomon Hospital. Pathological examination confirmed a silent FSH-producing pituitary adenoma. Forty-five patients less than 20 years old underwent transsphenoidal surgery for pituitary adenoma at Toranomon Hospital between 1993 and 2010. Of the 45 patients, 36 (80.0%) had clinically functioning adenomas and the other 9 (20.0%) had clinically non-functioning adenomas. No patients, other than the present case, had a silent gonadotroph adenoma. In contrast, among 579 patients over 20 years old undergoing surgery for nonfunctioning pituitary adenomas between 2006 and 2010 at Toranomon Hospital, 304 (52.3%) had silent gonadotroph adenomas. Gonadotroph adenomas are more common with aging: for example, 37 (61.7%) of 60 patients more than 70 years old at the time of operation had gonadotroph adenomas. In conclusion, gonadotroph adenomas, especially silent gonadotroph adenomas, are extremely rare in childhood and adolescence.     

Detection of Heterozygous Mutation in the Retinoblastoma Gene in a Human Pituitary Adenoma Using PCR-SSCP Analysis and Direct Sequencing

Genomic deoxyribonucleic acid from surgical specimens of 25 pituitary adenomas was screened for the presence of mutations in the tumor suppressor gene, retinoblastoma gene, using polymerase chain reaction and single-strand conformation polymorphism analysis, followed by direct deoxyribonucleic acid sequencing. Mutation causing an amino acid change was found in one of the 25 pituitary adenomas. The mutation site was in exon 19 (codon 621) of the retinoblastoma gene. In addition, there were three types of silent mutations in introns of the gene. The patient in whom the retinoblastoma mutation was identified had a tumor with high clinical malignancy, a high percentage of c-myc protein-labeled cells, and a diagnosis of plurihormonal pituitary adenoma based on the presence of cells immunoreactive for five pituitary hormones. This article suggests that point mutation of retinoblastoma gene is rare in human pituitary adenomas but may provide a marker for aggressive pituitary adenoma.     

Contribution of immunohistochemistry, electron microscopy, and cell culture to the characterization of nonfunctioning pituitary adenomas: A study of 40 cases

We studied 40 endocrinologically inactive pituitary adenomas by immunohistochemistry, electron microscopy, and cell culture in order to determine the incidence of gonadotropic adenomas and to classify nonfunctioning adenomas. Immunohistochemical studies using a large panel of monoclonal and polyclonal antibodies identified the following nonfunctioning adenomas: 20 gonadotropic adenomas, four silent corticotropic adenomas, one plurihormonal adenoma, and 15 nonsecreting adenomas. Among nonsecreting adenomas, ultrastructural study of 13 cases identified seven null cell adenomas and six oncocytomas. Silent corticotropic adenomas were classified into subtypes I, II, and III according to Kovacs and Horvath. Most often, gonadotropic adenomas displayed a varying number of oncocytic cells, characteristic secretory granules, and a prominent Golgi apparatus. Postembedding immunoelectron microscopy was performed on eight gonadotropic or nonsecreting adenomas, but this technique did not provide any additional information. Six gonadotropic adenomas and 10 so-called nonsecreting adenomas were studied in primary cell cultures. The six gonadotropic adenomas and seven of the 10 nonsecreting adenomas released gonadotropins in the culture medium. The use of in vitro results as a supplementary diagnostic criterion allowed classification of the 40 nonfunctioning adenomas as follows: 27 gonadotropic adenomas, four silent corticotropic adenomas, one plurihormonal adenoma, and eight nonsecreting adenomas. These results demonstrate a high proportion of gonadotropic adenomas among nonfunctioning adenomas (67.5%) and the usefulness of several techniques in characterizing this type of pituitary adenoma.     

Essential role of ultrastructural examination for spindle cell oncocytoma: Case report of a rare neoplasm and review of the literature

Spindle cell oncocytoma (SCO) is an extremely rare neoplasm of the sellar region recognized as a distinct benign histopathological subtype of pituitary tumors in the 2007 World Health Organization classification of tumors of the central nervous system. The morphology of its neoplastic cells (spindle cells and granular eosinophilic cytoplasm) is common to several other lesions so that immunohistochemistry, together with ultrastructural examination, becomes essential in solving this differential diagnosis. Despite being labeled as benign, recurrence is described. Herein, we report a case of SCO in a 77-year-old man and discuss the diagnostic difficulties, ultrastructural aspects, and prognostic factors.     

Ultrastructural Features of Apoptosis in Human Pituitary Adenomas

Although several recent studies deal with various molecular aspects of apoptosis, or programmed cell death, very little information is available on the ultrastructural changes associated with apoptosis in the adenohypophysis and its role in the regulation of pituitary adenoma growth and progression. This paper describes the distinct ultrastructural sequences that develop during the various phases of the apoptotic process. The study is based on the ultrastructural investigation of more than 8,000 surgically removed pituitary biopsies, which were examined by histology and immunocytochemistry for diagnostic purposes. No apoptosis was found in normal adenohypophysis and it is also a rare event in pituitary adenomas. When present, adenomatous adenohypophysial cells exhibit common and characteristic apoptotic changes. The ultrastructural alterations of membraneous organelles associated with apoptosis are similar to those previously reported in other tissues. It is noteworthy that apoptosis is clearly distinguishable from the ubiquitous dark cells denoting the common way of cell death. The findings suggest that apoptosis in pituitary adenomas is not a random event. Practically every specimen containing multiple apoptotic cells represents corticotroph adenoma. Occasional examples occur in lactotroph or gonadotroph adenomas. Although electron microscopic specimens are admittedly small, the large number of investigated cases gives credence to the observations.     

Localization of insulin-like growth factor-II mRNA in human pituitary adenomas

Insulin-like growth factors (IGFs) have been reported to promote cell proliferation in many tumours, but their contribution to pituitary adenoma development and growth has not been characterized. We report the presence of insulin-like growth factor II (IGF-II) mRNA in pituitary adenomas using in situ hybridization (ISH). The intensity of IGF-II hybridization signal was correlated with adenoma type, and the presence of Ki-67. Among the 109 adenomas examined, 55 (50.4%) were positive for IGF-II mRNA. All acidophil stem cell, functioning corticotrophic and plurihormonal adenomas contained the message; a high incidence of signal was found among sparsely (7/8) and densely (4/6) granulated growth hormone (GH) cell adenomas, mixed GH cell–prolactin (PRL) cell adenomas (6/7), thyrotrophic (4/6) and null-cell (6/7) adenomas. Less frequently, IGF-II mRNA was localized in mammosomatotrophic, silent subtype 3, gonadotrophic, and oncocytic adenomas, whereas all sparsely granulated PRL cell adenomas and silent corticotrophic adenomas of subtypes 1 and 2 were negative. The MIB-1 labelling index was significantly higher in adenomas with a moderate to intense IGF-II signal than in adenomas with weak or no signal. The results suggest that IGF-II, when highly expressed, may have a role in pituitary adenoma proliferation.     

Ultrastructural Features of Apoptosis in Human Pituitary Adenomas

Although several recent studies deal with various molecular aspects of apoptosis, or programmed cell death, very little information is available on the ultrastructural changes associated with apoptosis in the adenohypophysis and its role in the regulation of pituitary adenoma growth and progression. This paper describes the distinct ultrastructural sequences that develop during the various phases of the apoptotic process. The study is based on the ultrastructural investigation of more than 8,000 surgically removed pituitary biopsies, which were examined by histology and immunocytochemistry for diagnostic purposes. No apoptosis was found in normal adenohypophysis and it is also a rare event in pituitary adenomas. When present, adenomatous adenohypophysial cells exhibit common and characteristic apoptotic changes. The ultrastructural alterations of membraneous organelles associated with apoptosis are similar to those previously reported in other tissues. It is noteworthy that apoptosis is clearly distinguishable from the ubiquitous dark cells denoting the common way of cell death. The findings suggest that apoptosis in pituitary adenomas is not a random event. Practically every specimen containing multiple apoptotic cells represents corticotroph adenoma. Occasional examples occur in lactotroph or gonadotroph adenomas. Although electron microscopic specimens are admittedly small, the large number of investigated cases gives credence to the observations.