Structure-function correlations of human pituitary gonadotroph adenomas in vitro

Two pituitary gonadotroph adenomas were studied in vitro to characterize structure-function correlations. Both tumors were from men, aged 63 and 69 years, who had elevated blood levels of follicle-stimulating hormone (FSH) and normal blood luteinizing hormone (LH) and testosterone values. The surgically resected adenomas contained diffuse immunohistochemical positivity for beta-FSH, beta-LH, and alpha-subunit of glycoprotein hormones; by electron microscopy they were composed of well-differentiated gonadotrophs. In vitro, both tumors released FSH, LH, and alpha-subunit. Morphometric studies were performed on surgically resected and cultured adenoma cells. Compared with the surgical specimens, the cultured cells had decreased cytoplasmic volume densities of endoplasmic reticulum and Golgi apparatus and slightly increased cytoplasmic volume densities of secretory granules. Incubation with gonadotropin-releasing hormone (GnRH) for 2 and 24 hours increased FSH, LH, and alpha-subunit release by both tumors; morphometry after 2 consecutive days of exposure confirmed significant increases in cytoplasmic volume densities of endoplasmic reticulum and Golgi regions and marked decreases in that of secretory granules. There was no significant change in cell size, nuclear/cytoplasmic ratio, or secretory granule diameter. The two tumors differed in their response to gonadal steroids. Estradiol, testosterone, and progesterone stimulated release of FSH, LH, and alpha-subunit by one tumor and the morphologic changes paralleled the biochemical response; addition of testosterone suppressed the secretory and morphologic response to GnRH. The other tumor showed no significant response to estradiol or testosterone and addition of these steroids did not alter the response to GnRH. The results are consistent with the interpretation that GnRH stimulates not only release but also synthesis of gonadotropins by gonadotroph adenomas of men. The data also indicate variable sensitivity of these tumors to gonadal steroids with paradoxical stimulation alone and inhibition of response to GnRH. The structural changes correlate with the hormone release response in vitro.     

Androgen receptor in pituitary adenomas of the gonadotroph cell complex

Although androgen receptors have been identified in normal gonadotroph and somatotroph cells of the pituitary, immunohistochemical studies have failed to reveal these receptors in pituitary adenomas so far. Using a monoclonal antibody to androgen receptor in our series of 60 adenomas of the gonadotroph cell complex (20 FSH/LH cell adenomas, 20 null cell adenomas, 20 oncocytic adenomas), only one null cell adenoma showed strong nuclear immunostaining. All the other antibodies were completely negative. The significance of this finding in correlation with clinical data is still unclear, although it may be associated with more rapid tumor growth. In paraadenomous tissue, some normal gonadotrophs expressed the androgen receptor.     

Human pituitary gonadotroph adenomas: Relationship between gonadotropin immunoreactivity and clinicopathologic findings

Clinically nonfunctioning pituitary adenomas are generally seen in middle-aged and older patients, and most of them may be gonadotropin-immunoreactive adenomas, that is, gonadotroph adenomas. Our aim was to clarify the relationships between the gonadotropin immunoreactivity, patient age, sex, and microscopic features in 68 gonadotroph adenomas with special reference to either gonadotropin-immunonegative or intensively immunopositive adenomas. There were 68 patients with gonadotroph adenomas (mean age 54.7 yr) in the study, including 39 men (mean age, 52.8 yr) and 29 women (mean age, 57.4 yr). The adenomas were diagnosed on the basis of immunoreactivity for gonadotropins (β-subunit of follicle-stimulating hormone: β-FSH; β-subunit of luteinizing hormone: β-LH; and the α-subunit of the pituitary glycoprotein hormone: α-SU) by the avidin-biotin peroxidase complex (ABC) method or by the characteristic histological feature of a perivascular or pseudorosette pattern, that is, the cells aligned polarity directed toward the capillaries. Fifty-four adenomas (79%) were positive for one or more gonadotropin subunits and β-FSH was the most common subunit encountered (47/68, 69%). In men β-FSH immunoreactivity was similar among all age groups, whereas in women, it was significantly less frequent in patients who were 50 yr or older, compared to younger patients. Gonadotropin-immunonegative adenomas were seen in 4 men (mean age, 46.8 yr) and 10 women (mean age, 61.5 yr). Among the 22 women aged 50 or over, β-FSH was negative in 12 tumors (55%), whereas in men of the same age group, it was negative in 3 of 26 tumors (12%). The reason for this reduced frequency is not clear, but the postmenopausal state and associated changes in the systemic endocrine state may play a role. Adenomas that were intensively positive for β-FSH showed an unusual morphology other than the characteristic perivascular pattern, regardless of the patients' age and sex; the tumor cells had abundant vacuolated cytoplasms and were arranged in a sheet-like pattern. Electron microscopically, these cells with abundant cytoplasm had well-developed Golgi complexes, suggesting an enhanced activity of gonadotropin synthesis, and these adenomas seem to be endocrinologically, if not clinically, functioning. The results indicate that gonadotroph adenomas may vary from functioning adenomas with intense immunoreactivity and unusual histology to immunonegative and less functioning adenomas, which are more frequent in women 50 yr or older.     

Null cell adenomas,oncocytomas, and gonadotroph adenomas of the human pituitary: An immunocytochemical and ultrastructural anafysis of 300 cases

The immunocytochemical profile of 300 clinically nonsecreting pituitary adenomas was investigated. All tumors were diagnosed, classified, and separated into null cell adenomas, oncocytomas, and gonadotroph adenomas according to their ultrastructural morphology. The immunocytochemical analysis was based on the semiquantitative proportional estimates of positive cells immunostained for all known peptide and glycoprotein pituitary hormones including alpha-subunit. The majority of tumors (87%) were to some extent immunopositive for various hormones. Glycoprotein hormones were most frequently encountered. Usually, particularly in males, more than one subunit was present in the same tumor. In 97 tumors (32%) more than 25% of adenoma cells were immunoreactive for gfycoprotein hormones. Fifty-five tumors (18%) contained occasional cells immunopositive for growth hormone (GH), prolactin (PRL), and adenocorticotropin (ACTH) in addition to glycoprotein hormones. Given the significant proportion of immunoreactive cells for gonadotropins and alpha-subunit, in tumors characterizedas null cell adenomas and oncocytomas, imrnunocytochemistry may provide valuable information to the pathologist and clinical endocrinologist contributing to the evaluation of this heterogeneous group of tumors.     

GH-, PRL-, POMC-, beta-TSH-, beta-LH-, beta-FSH-mRNA in gonadotroph adenomas of the pituitary by in situ hybridization in comparison with immunostaining and clinical data

In situ hybridization (ISH) enables the visualization of specific mRNA for pituitary hormones. Our collection consists of 40 surgically removed pituitary adenomas that were classified as follicle stimulating hormone/luteinizing hormone (FSH/LH) cell adenomas by structure and by immunostaining (IH) for all pituitary hormones. All forty adenomas were regarded as clinically inactive. The aim of our study was to examine nonfunctioning adenomas by ISH for demonostration of mRNAs for all pituitary hormones. The results were compared with proliferation markers, invasiveness and clinical data. ISH detected signals for all pituitary hormones at a range of 30% for prolactin (PRL) to 85% for proopiomelanocortin (POMC). mRNA for β-FSH was detected in 70% and β-LH mRNA in 43% of adenomas. Thirty-three percent of adenomas revealed negative mRNA detection for β-LH but positive hormone content. The majority of adenomas (75%) expressed more than two mRNAs simultaneously, mostly the combination of POMC mRNA together with β-FSH mRNA and one to four others. Comparison with clinical data showed no significant differences except for one adenoma with a high Ki-67 index (>2.1% positive nuclei). This adenoma showed very high signals for PRL and β-TSH mRNA.     

Spontaneous pituitary gonadotroph nodules in aging male Lobund-Wistar rats

Spontaneous pituitary changes with aging were studied in 130 male Lobund-Wistar rats by light and electron microscopy and immunohistochemistry. These 69 healthy rats (6, 18, and 30 months) and 61 moribund rats (17-50 months) had been maintained in four different groups with the following environmental conditions: conventional full fed, convention food restricted, germ free-full fed, and germ free-food restricted. Gonadotroph nodules were the most frequent proliferative lesions (27 rats). It was difficult to determine whether these nodules were hyperplastic or neoplastic. They were found in aging rats (26 months or older) and their development was delayed by food restriction and germ-free status parallel to prolongation of life-span. No significant difference in incidence of gonadotroph nodules was demonstrated among the four groups. Six lactotroph adenomas, a thyrotroph nodule, and a mixed thyrotroph and lactotroph nodule were also noted in aging rats (30 months or older). In extranodular adenohypophyses, variable numbers of hyperactive gonadotrophs histologically similar to those in gonadotroph nodules were observed in almost all rats including 6-month rats, suggesting that gonadotrophs were continuously hyperactive during their lifetime from an early stage. The mechanism accounting for the development of gonadotroph nodules remain to be established. It can be concluded that food restriction and germ-free status may have a retarding effect but no preventative role in the development of gonadotroph nodules, which are the most common age-associated pituitary lesions of male Lobund-Wistar rats.     

A clone of elusive parents: gonadotroph adenoma-female type

A 69-year-old woman presented with visual disturbance. Perimetry testing revealed a bitemporal hemianopia. Brain MRI demonstrated a 2.2-cm gadolinium-enhancing pituitary mass. Previously she had been treated for hypothyroidism, hypertension, and dyslipidemia. She had hyperprolactinemia. Endoscopic transsphenoidal debulking improved her visual field defects. Histology showed a chromophobic adenoma. Electron microscopy showed elongated, polar cells with long, slender processes. The small uniform secretory granules were peripherally disposed, collecting heavily within cell processes. Based on electron microscopical characteristics the tumor is consistent with an ACTH-negative female gonadotroph adenoma. The parent cell of this rare variant of a pituitary adenoma is yet unknown.     

Amyloid in pituitary adenomas

71 surgically removed pituitary adenomas with amyloid deposits were studied by light microscopical and immunohistological means. In none of the adenomas was there a predominance of amyloid deposits. There were no correlations between the extent or pattern of the deposits with either age, immunohistological hormone content or localization. Our results do not support either of the theories about the origin of amyloid--whether mesenchymal or produced by adenoma cells--in pituitary adenomas.     

Pituitary adenomas

Human pituitary adenomas are benign neoplasms composed of hormonal adenohypophyseal cells. They arise in the sella turcica, and are characterized by a wide range of biological behavioral related not only to hormonal but also to proliferative activities. In the past, pituitary adenoma studies have mainly been devoted to histological and ultrastructural classification improved by immunohistochemical techniques. Molecular biology, cytogenetic studies, associated to experimental animal models, transgenic and knockout mice technologies, have allowed new approaches, especially concerning pathogenesis and progression. It became obvious that tumorigenesis has to be considered as a multistep event, inasmuch as different factors share numerous homologies. On the other hand, it could be supposed that the knowledge of the biological aggressiveness could led to an appropriate follow-up as well as specific therapy.     

Pituitary adenomas

This review highlights various aspects of the new functional classification of pituitary adenomas which is based on detailed immunohistochemical and ultrastructural analysis and correlation with clinical and biochemical findings. In addition, current investigation of the non-hormonal aspects of these tumours is discussed, including the application of flow cytometry in tumour ploidy studies.     

Immunolocalization of beta-catenin in pleomorphic adenomas and carcinomas ex-pleomorphic adenomas of salivary glands.

Beta-catenin plays a central role in cadherin/catenin cell-cell adhesion complex and is involved in cell signaling pathway. Change in beta-catenin distribution has been associated with several human cancers including salivary gland tumors. We studied the immunolocalization of beta-catenin in a series of pleomorphic adenomas (PA) and carcinomas ex-pleomorphic adenomas (Ca ex-PA). Ten samples of PA and ten of Ca ex-PA were evaluated by immunohistochemistry using streptavidin-biotin-peroxidase technique and a monoclonal antibody against beta-catenin (E-5). Cell membrane/cytoplasmic staining of beta-catenin was observed in normal gland parenchyma, PA, and in well-differentiated Ca ex-PA. Cytoplasmic/nuclear beta-catenin staining was observed in poorly differentiated carcinomas and, interestingly, in one case of PA. Our data showed decreased cell membrane beta-catenin expression in higher-grade tumors suggesting that beta-catenin may play an important role in histologic differentiation and transition to malignant phenotype of Ca ex-PA.     

Grading of pituitary adenomas in acromegaly

Summary In a series of 284 adenomas from cases of acromegaly we studied major morphological variables using light microscopical techniques and compared them with immunocytochemical and clinical results.Using our semiquantitative estimations many inter-relationships were observed. We established the density of secretory granules, nuclear pleomorphism and the rate of occurrence of multinuclear tumour cells, as essential features of tumour differentiation. Mitotic activity and invasive growth patterns did not reveal clear dependences.Immunocytochemical analysis of 105 cases showed growth hormone (GH) in nearly all adenomas (98%), prolactin in 68%, and LH in 40%. The other hormones (ACTH, FSH, and TSH) were present at a much lower rate. Monohormonal GH-adenomas were found in only 29% of our cases.Many different combinations of hormone content could be demonstrated without any relationship to morphological or clinical data. From the linear correlations and advanced method of semiquantitative evaluation, the granular density of the tumour cells is the most useful variable for subclassification and grading of pituitary adenomas in acromegaly.This publication contains results from the doctorthesis submitted by M. Riedel (Hamburg 1984)     

Neuroendocrine cells in colorectal adenomas

A consecutive series of 218 endoscopically resected colorectal adenomas was investigated for the occurrence of neuroendocrine cells. In 59 per cent of these adenomas argyrophil cells were detected. In 8 per cent of the adenomas these cells were numerous and so intricately blended in with the other cell types that they were regarded as an intrinsic part of the tumour. In these adenomas subsequently immunocytochemistry revealed the presence of the neuro-hormonal peptides glucagon, pancreatic polypeptide and somatostatin as well as serotonin, in a pattern similar to that seen in normal colorectal mucosa. The presence of neuroendocrine cells did not correlate with any clinical or pathological parameter. The occurrence of neuroendocrine cells in colorectal adenomas is in agreement with the unitarian theory of the development of the various epithelial cell types in large bowel mucosa.     

Atypical mitoses in colorectal adenomas

The frequency of spontaneously occurring mitotic figures, the proportion atypical mitoses and spatial position (vertical, oblique or horizontal) of metaphasial plates were studied in 62 specimens: 47 with colorectal adenomas, and 15 with chronic ulcerative colitis (control cases). The characteristics of the atypical mitoses at pro-phase, pro-metaphase, metaphase, anaphase and telophase were defined and illustrated. The results indicated that atypical mitoses occurred in 8.9% in control patients, in 37.2% of the specimens tubular adenomas having low-grade dysplasia, in 80.8% in tubular adenomas with high-grade dysplasia, in 68.5% of villous adenomas with low-grade dysplasia and in 65.5% of villous adenomas with high-grade dysplasia. For villous adenomas with high-grade dysplasia having invasive growth, 81.3% of atypical mitoses was recorded. Oblique or horizontal metaphasial plates were present in 8% of the metaphases in control cases but in as much as 25% in tubular adenomas with low-grade dysplasia, in 37% of those with high-grade dysplasia, in 42% for villous adenomas with low-grade dysplasia, in 56% for those with high-grade dysplasia and in 53% for villous adenomas with invasive growth. The classification of the various degrees of dysplasia is at present done by the characteristic of the dysplastic cells at interphase. This paper demonstrates that qualitative and quantitative morphological alterations of the mitotic apparatus takes place in the various histological types of colorectal adenomas. Perhaps both the number of atypical mitoses and the spatial position of the mitoses should be registered in attempts to shed more light on the biological behaviour of adenomatous lesions of the colorectal mucosa.     

CD markers in pituitary adenomas

Immunostaining of CD markers in normal pituitary cells has been reported, but a study of these markers in pituitary adenomas has not been done. The expression of CD 3, CD 8, CD 15, CD 20, CD 30, CD 43, CD 45R0, CD 45 R, CD 79 α, and VS-38c was investigated in a collection of 65 pituitary adenomas of various types. CD 3 was present in 75%, CD 8 in 18.5%, CD 15 in 12.3%, CD 20 in 66.1%, CD 30 in 10.8%, CD 43 in 10.8%, CD 45 RO in 72.3%, CD 45 R in 16.9%, CD 79α in 0% and VS-38 c in 44.6%. Densely granulated GH cell adenomas expressed CD 3, CD 20, CD 45 RO, and CD 45 R, but no other markers. Sparsely granulated GH cell adenomas showed CD 3, CD 8, CD 20, CD 43, and CD 45 RO. Mixed GH/prolactin cell adenomas contained CD 3, CD 8, CD 20, CD 30, CD 45RO, CD 45 R, and VS-38c. Mammosomatotroph cell adenomas were positive only for CD 3, CD 8, CD 20, CD 43, and CD 45 RO. Prolactin cell adenomas expressed CD 3, CD 8, and CD 20. ACTH cell adenomas showed CD 3, CD 15, CD 20, CD 30, CD 45 RO, CD 45 R, and VS-38c. TSH cell adenomas contained CD 3, CD 8, CD 15, CD 20, CD 45 RO, and VS-38c. Gonadotroph cell adenomas were positive for CD 3, CD 8, CD 20, CD 45 RO, CD 45 R, and VS-38c. Alpha-subunit-only adenomas expressed CD 3, CD 8, CD 15, CD 20, CD 30, CD 45 RO, and VS-38c. Plurihormonal adenomas contained CD 3, CD 8, CD 20, CD 30, CD 43, CD 45 RO, CD 45 R, and VS-38c. Oncocytic adenomas were positive for all markers except CD 45 RA and CD 79 α. We conclude that the spectra of different adenoma types expressing CD markers varies greatly and that significant correlations do not exist, although noninvasive adenomas appear to express CDs more frequently than invasive adenomas. We have no clear-cut explanations for the various expressions and suggest that it may be a sign of local interactions between the immune system and pituitary adenomas.