Coexpression of galanin and adrenocorticotropic hormone in human pituitary and pituitary adenomas.

Galanin is a neuropeptide that regulates the secretion of several pituitary hormones, including prolactin (PRL) and growth hormone (GH). Galaninlike immunoreactivity (Gal-IR) and galanin mRNA in the rat anterior pituitary is cell lineage specific, with predominant expression in lactotrophs and somatotrophs. The authors examined the cellular distribution of human Gal-IR in seven normal postmortem pituitaries and 62 pituitary tumors by immunoperoxidase staining. In contrast to the rat, Gal-IR in human anterior pituitaries was present in corticotrophs scattered throughout the gland, but not in lactotrophs, somatotrophs, thyrotrophs, or gonadotrophs. Distinct Gal-IR also was present in hyperplastic and neoplastic corticotrophs in 19 of 22 patients with Cushing's disease. In noncorticotroph cell tumors, unequivocal Gal-IR was present in 5 of 11 GH-secreting tumors associated with clinical acromegaly, 9 of 18 nonfunctioning pituitary adenomas, and 2 of 14 prolactinomas. Of these galanin-positive tumors, four of the five GH-secreting adenomas, six of the nine nonfunctioning adenomas, and both of the prolactinomas also contained adrenocorticotropic hormone immunoreactivity (ACTH-IR). Immunostaining and in situ hybridization on adjacent sections using an 35S-labeled probe complementary to human galanin mRNA demonstrated predominant galanin expression in normal corticotrophs. Immunoelectron microscopy confirmed the presence of Gal-IR in pituitary cells characteristic of corticotrophs in both normal and neoplastic pituitaries. Thus, as in the rat, galanin gene expression in the human pituitary is cell-type specific. Unlike the rat, however, human galanin gene expression is restricted to the corticotroph lineage. Studies of tumors confirmed the observed coexpression of galanin and adrenocorticotropic hormone. The divergent cell type specificity of galanin production in human and rat pituitaries reflects different patterns of gene activation in these two species. In addition, these results suggest that galanin in the human pituitary may participate locally in the regulation of the hypothalamic-pituitary-adrenal axis.     

Corticotroph (Basophil) invasion of the pars nervosa in the human pituitary: Localization of proopiomelanocortin peptides,galanin and peptidylglycine α-amidating monooxygenase-like immunoreactivities

Corticotroph (basophil) invasion or the migration of corticotroph cells into the pars nervosa of the human pituitary gland was found in 35 of 767 (4.4%) consecutive pituitaries obtained at autopsy. The degree of invasion increased with patient age and extensive invasion was more common in men than in women. Immunoreactive ACTH, β-MSH, α-MSH, and galanin were detected both in the anterior lobe and invading corticotroph cells in approximately equal frequency. Fewer cells stained positively for α-MSH than for the three other peptides in both the anterior lobe and invading corticotrophs. Twelve corticotropic pituitary adenomas obtained surgically from patients with Cushing’s disease were also examined and expressed varying degrees of immunoreactivity for ACTH, α MSH, β-MSH and galanin. Staining for all major pituitary hormones revealed only ACTH in the invading basophil cells. Peptidylglycine α-amidating monooxygenase (PAM) was present in the anterior pituitary, in invading corticotroph cells, and in some cells lining the cysts of the pars intermedia zone. PAM immunoreactivity was also detected in 4/12 corticotroph adenomas. These results indicate that corticotroph cells invading the pars nervosa are immunohistochemically similar to anterior lobe corticotrophs and have the ability to amidate various peptides such as proopiomelanocortin cleavage products and galanin with PAM.     

In situ hybridization study of pro-opiomelanocortin (POMC) gene expression in human pituitary corticotrophs and their adenomas

Summary Pro-opiomelanocortin (POMC) mRNA was detected on paraffin sections by in situ hybridization (ISH) in corticotrophs of 12 nontumorous pituitaries, 11 functioning corticotroph, and 11 silent pituitary adenomas. ISH combined with immunocytochemistry for adrenocorticotrophic hormone (ACTH), a POMC-derived peptide, was also performed. ACTH immunoreactive cells of the anterior lobes and those invading the posterior lobe showed a high or moderate level of POMC mRNA that was not correlated with the intensity of ACTH immunoreactivity. Variable levels of POMC gene expression were present in Crooke's cells, corticotrophs suppressed by glucocorticoid excess. Most functioning corticotroph adenomas and silent subtype 1 adenomas had an intense hybridization signal and ACTH immunoreactivity. In silent subtype 2 and 3 adenomas, POMC mRNA had a diffuse low level or was absent; in these adenomas ACTH immunoreactivity was diffuse, restricted to some cells, or negative. The results indicate that POMC gene is expressed in both normal and suppressed nontumorous corticotrophs. Intense signals for POMC mRNA are found in most functioning corticotroph adenomas. The difference between POMC gene expression in silent 1 and silent 2 and 3 adenomas suggests that different mechanisms are responsible for the lack of endocrine activity.     

Identification of corticotrophs in the human pituitary with mAB lu-5, a novel immunocytochemical marker

The presence of mAB lu-5, a panepithelial, monoclonal antibody was studied in human adenohypophyses and pituitary adenomas by immunohistochemistry using the avidinbiotin-peroxidase complex technique. In nontumorous adenohypophyses, only corticotrophs showed strong immunoreactivity, whereas other adenohypophysial cell types exhibited little or no staining. Positive immunostaining was observed in corticotrophs spreading to the posterior lobe, in cells of squamous nests located in the pars tuberalis and several cells lining pars intermedia cavities. The Crooke's hyaline material in the cytoplasm of corticotrophs was immunopositive. In adenomatous corticotrophs and cytoplasmic fibrous bodies of sparsely granulated adenomatous somatotrophs, distinct mAB lu-5 immunoreactivity was evident. GH-, PRL-, TSH-, FSH-, LH-, alpha-subunit-producing adenomas, null cell adenomas and oncocytomas showed no convincing staining. Immunopositivity in corticotroph adenomas was diffusely distributed in the cytoplasm and was not located in secretory granules, indicating that mAB lu-5 did not stain ACTH. Immunoreactivity with mAB lu-5 was not specific for pituitary corticotrophs, since the antibody stained nontumorous epithelial cells and epithelial tumor cells in other organs as well. It can be concluded that mAB lu-5 is a valuable immunocytochemical marker in pituitary related studies, especially in those pituitary adenomas in which immunostaining for ACTH is weak or equivocal; in these cases, it can confirm the diagnosis of corticotroph adenoma. The antibody yields similar results as keratin antisera. In our experience, however, it gives a stronger, more distinct immunopositivity with less nonspecific background staining.     

Clinicopathologic correlations of silent corticotroph adenomas of the pituitary: report of four cases and literature review

Silent corticotroph adenomas (SCA) are rare pituitary tumors with histologic hallmarks of corticotroph differentiation, including ACTH immunoreactivity, but lacking clinical evidence of Cushing's syndrome. We report on four female patients, aged 19-66 years, each presenting with a nonfunctional macroadenoma. Leading symptoms were headache in two cases and visual field deficits in one. One patient was incidentally diagnosed while undergoing cranial MRI for an unrelated condition. Three patients had marked obesity; none of them presented constitutional signs of Cushing's syndrome. Serum cortisol levels were moderately elevated in the two patients systematically tested in this respect. Marginal to moderate hyperprolactinemia was present in two cases. Two patients also were shown to be deficient in either gonadotroph or thyrotroph axis, while a third had a combined insufficiency of both gonadotroph and thyrotroph axis. MRI scans revealed intratumoral hemorrhage and/or cystic change in three cases, as well as tumor-related occlusive hydrocephalus in one. The latter patient was biopsied only, while the remaining underwent gross total resection. Histologically, all four lesions were diagnosed as SCA subtype I displaying intense immunoreactivity for ACTH. In three tumors, scattered cells coexpressed PRL as well. In addition, Crooke's hyaline change was noted in a significant number of tumor cells and in residual non-neoplastic corticotrophs in one case each. With MIB-1 labeling indices of 1-3%, none of the tumors qualified as atypical adenoma. We conclude that SCAs are more likely to be discovered as expansile tumors, whose advanced local space-occupying character at surgery rather than an inherently aggressive growth potential may negatively influence the clinical outcome. Subtle morphologic evidence of corticotroph suppression in residual pituitary adjacent to tumor lends further support to literature data indicating minimal or intermittent functional activity in this tumor type.     

Localization of Epidermal Growth Factor (EGF) and Epidermal Growth Factor Receptor (EGFr) in Human Pituitary Adenomas and Nontumorous Pituitaries: An Immunocytochemical Study

Epidermal growth factor (EGF) and epidermal growth factor receptor (EGFr) were investigated by immunocytochemistry (ICH) in 57 human pituitary adenomas and 10 nontumorous autopsy pituitaries. EGF immunoreactivity was demonstrated in 24 adenomas (42%), representing 23 functioning tumors and 1 nonfunctioning tumor of oncocytic type, and in all nontumorous pituitaries. Among 40 tumors, EGFr was found positive in 15 functioning adenomas (37.5%), representing 50% of them. The presence of both EGF and EGFr was found mainly in corticotroph adenomas (60%) and less frequently in somatotroph and lactotroph adenomas (20%). ICH on serial sections with EGF or EGFr and adrenocorticotrophic hormone (ACTH) or S-100 protein revealed that EGF and EGFr are localized specifically in corticotrophs and EGFr in stellate cells of nontumorous adenohypophysis. These results confirm the presence of EGF and EGFr in human pituitary adenomas and nontumorous pituitaries and highlight their frequent occurrence in hormone-producing adenomas. Further work is required to explore the possibility that EGF and EGFr play a role in hormone production, release, and tumor progression.     

Immunohistochemical Expression of Neuroendocrine Secretory Protein-55 (NESP-55) in Pituitary Adenomas

Neuroendocrine secretory protein-55 (NESP-55) is a recently described member of the chromogranin family and appears to be a marker of the constitutive secretory pathway in certain neural, neuroendocrine, and endocrine cell types. It has been shown to be selectively expressed in tumors differentiating towards the adrenal chromaffin and pancreatic islet cell phenotypes. The highest levels of NESP-55 expression, at least in animals, appear to be in the adrenal medulla and the pituitary gland. However, very little is known about the status of NESP-55 expression in pituitary adenomas. We therefore studied the immunohistochemical profile of NESP-55 expression in a series of 30 well-characterized pituitary adenomas (five each of FSH/LH and ACTH, four GH, three TSH, seven prolactin, and six null cells). All tumors were positive for one or more generic marker(s) (chromogranin A, synaptophysin, neuron-specific enolase) of neuroendocrine differentiation. All pituitary adenomas selected for study were stained for NESP-55 with appropriate positive and negative controls. NESP-55 immunoreactivity, seen as brown finely granular cytoplasmic staining of the tumor cells with prominent perinuclear accentuation, was graded as focal (<10% tumor cells staining), moderate (10–50% tumor cells staining), and diffuse (>50% tumor cell staining). Four of seven prolactinomas were positive for NESP-55 (one focal, two moderate, and one diffuse). Two of four GH adenomas were also positive (one focal and one diffuse) while only 1/5 FSH tumors showed a moderately intense immunoreactivity. All other pituitary adenomas were completely negative for NESP-55. Our results indicate that, in human pituitary adenomas, NESP-55 has a more restricted pattern of expression than that of chromogranins A and B. Since immunohistochemical expression of NESP-55 is largely confined to prolactinomas and GH adenomas, it raises the possibility that NESP-55 may somehow be involved in the secretory pathways of these specific cell types.     

Immunocytochemical demonstration of intermediate filament cytoskeleton proteins in human endocrine tissues and (neuro-) endocrine tumours

Summary The presence and distribution of intermediate filament proteins, such as cytokeratins, vimentin, neurofilament proteins and glial fibrillary acidic protein were assessed immunohistochemically in pituitary adenomas, medullary thyroid carcinomas, endocrine pancreatic tumours, gastric, intestinal and bronchial carcinoids, parathyroid adenomas, pheochromocytomas, paragangliomas and related non-neoplastic tissues. In some cases, immunohistochemical results were correlated with cytoskeletal proteins as analysed by SDS-polyacrylamide gel electrophoresis. Cytokeratin antibodies with broad range of immunoreactivity (i.e. to murine liver cytokeratin component D) reacted with epithelial cells in all non-neoplastic endocrine tissues and related neuroendocrine tumours studied, except for adrenal medulla, pheochromocytoma and paraganglioma, independently of hormone production and biological behaviour. In contrast, antibodies to epidermis-derived cytokeratins failed to stain endocrine tissues and tumours. Paranuclear cytokeratin accumulations were seen in bronchial, gastric, and intestinal carcinoids and seem to be a common feature of neuroendocrine tumours. One-and two-dimensional SDS-polyacrylamide gel electrophoresis of non-neoplastic endocrine tissues and related tumours revealed two major keratin polypeptides corresponding to cytokeratins No. 8 and 18 of the cytokeratin catalog of human cells (Moll et al. 1982). According to this cytokeratin polypeptide composition, endocrine tissues and related tumours conform to the simple type of epithelia. Vimentin-related immunoreactivity was restricted to stromal cells and to folliculo-stellate cells in normal pituitary gland, Schwann cells in carcinoids and satellite cells in normal adrenal medulla and in pheochromocytomas. Neurofilament protein- (70 kD)-antibodies only stained nerve fibers in normal tissues and at the periphery of carcinoid tumour cell complexes, and, to a variable degree, cells in nontumorous adrenal medulla, pheochromocytomas and paragangliomas. Furthermore, neurofilament reactivity was observed along with cytokeratin expression in two bronchial carcinoids.     

Crooke's hyalinization in silent corticotroph adenoma: report of two cases

Corticotroph adenomas rarely show Crooke’s hyaline change in neoplastic cells, a feature similar to that of normal corticotroph cells exposed to excess cortisol. Crooke’s cell adenomas are usually associated with Cushing’s disease. Nonfunctioning examples are uncommon. We report two clinically silent corticotroph adenomas featuring extensive Crooke’s hyalinization in neoplastic cells. The two patients were 49 and 59 yr of age and neither had Cushing’s disease. Serum and urinary cortisol were normal. One patient had elevated serum adrenocorticotropic hormone. In our experience, the two patients accounted for 0.4% of pituitary adenomas operated on from January 1992 to December 2001 and 3.5% of all corticotroph adenomas. The two lesions had features of the subtype 1 silent corticotroph adenoma. Cytogenetic analysis performed on one lesion showed a normal karyotype (46;XY). Hyalinization in clinically silent Crooke’s cell adenoma indicates that hyaline changes do not always relate to excess cortisol. It is known that neoplastic Crooke’s cells show immunoreactivity for glucocorticoid receptors stronger than nontumorous Crooke’s corticotrophs. This fact suggests that receptor overexpression or lack of receptor downregulation may result in hypersensitivity of neoplastic Crooke’s cells to physiologic cortisol plasma levels.     

A study of intermediate lobe differentiation in the human pituitary gland

The immunohistochemical demonstration of neurofilament (NF) polypeptide was used to identify nerves in a series of 17 pituitary adenomas. NF-positive fibres were present in two out of five corticotroph adenomas sited deep in the anterior lobe, in one out of five sited in the intermediate zone and in two out of seven non-corticotroph adenomas. Such nerve fibres were often seen in relation to blood vessels. The distribution of alpha-MSH immunoreactive cells was examined in 25 normal pituitaries and in 23 cases of Cushing's disease. Such cells were scattered throughout the normal gland and there was no increase in numbers in pregnancy. alpha-MSH was demonstrated in 18 corticotroph adenomas in Cushing's disease. There was no correlation with the site of the tumour or the presence of nerve fibres. alpha-MSH cells were distributed normally in the para-adenomatous gland. Crooke's hyaline change and alpha-MSH coexisted in some corticotrophs. These findings support the concept that 'intermediate lobe' function, as found in animals, has no discrete anatomical location in man.     

Expression of opioid peptides in tumors

We looked for opioid peptides and their precursors in 108 tumors of both neuroendocrine and nonneuroendocrine origin, using a monoclonal "pan-opioid" antibody, 3-E7, which recognizes the tetrapeptide Tyr-Gly-Gly-Phe (the sequence responsible for pharmacologic activity in all known opioid peptides), in conjunction with polyclonal antibodies directed against representative peptides of each of the three precursors (alpha-endorphin, [met]enkephalin-Arg-Gly-Leu, and dynorphin B). Using the avidin-biotin immunoperoxidase technique, we observed consistent cytoplasmic immunoreactivity (at least focally) in all of 15 adrenal pheochromocytomas, all of 6 thyroid medullary carcinomas, and all of 5 pituitary adenomas. Opioid staining was also observed in parathyroid adenomas (8 of 9), pancreatic islet-cell tumors (7 of 10), carcinoid tumors from various sites (18 of 26), and paragangliomas (1 of 2). There was no immunoreactivity in pulmonary small-cell carcinomas, Merkel-cell tumors of skin, neuroblastomas, or any of the non-neuroendocrine tumors examined. The expression of alpha-endorphin, [met]enkephalin-Arg-Gly-Leu, and dynorphin B varied from tumor to tumor; however, positive staining with the "pan-opioid" antibody was found in each tumor containing at least one of the three precursors. Opioid peptide immunoreactivity was also detected in non-neoplastic cells of the adrenal medulla, pancreatic islets, pituitary, intestinal and bronchial mucosa, and intestinal myenteric plexuses. We conclude that opioid expression within tumors is most likely due to enhanced expression of a normal cell product and that opioid peptides are useful markers of neuroendocrine differentiation in many tumors.     

Histidine decarboxylase expression in pancreatic endocrine cells and related tumors

Histidine decarboxylase (HDC) is an enzyme for decarboxylating l-histidine to histamine and is expressed in various types of cells including neuroendocrine tumors. Recent findings have demonstrated a high percentage of HDC immunoreactivity in many neuroendocrine tumors, including carcinoid tumors, small cell carcinomas of the lung, pheochromocytomas, and medullary carcinomas of the thyroid. HDC immunostaining was applied to pancreatic islet cells and related tumors to explore possible expression of HDC as a wide spectrum marker for neuroendocrine differentiation. A total of 24 cases (22 pancreatic endocrine neoplasms, one small cell carcinoma of the pancreas, and one mixed exocrine-endocrine carcinoma) along with normal pancreatic tissue were immunostained with the anti-HDC antibody. In a normal pancreas, a double immunostaining revealed possible colocalization of HDC with glucagon- or insulin-positive cells in the islets. Seventeen of 22 pancreatic endocrine neoplasms (77%) were found to be positive for HDC, and no distinct relation to hormonal activity was observed. One small cell carcinoma was strongly positive to HDC. One non-functional tumor with mixed exocrine and endocrine components showed a diffuse positive immunostaining for HDC, and some neoplastic glucagon- or somatostatin (SRIF)-positive cells coexpressed HDC. In conclusion, we demonstrated that the majority of pancreatic endocrine tumors expressed HDC, and we suggest that HDC is a wider new marker for neuroendocrine differentiation.     

The Immunophenotype of Pituitary Adenomas

Although the production of pituitary hormones by adenohypophysial tumors has been studied extensively, an examination of the immunophenotype of pituitary adenomas using a broad spectrum of antibodies has not been previously investigated. We studied 23 pituitary adenomas using a large panel of antibodies to determine if these tumors exhibited a common immunophenotype. Various neuroendocrine markers, synaptophysin, neuron-specific enolase (NSE), and the intermediate filament protein, low-mol-wt keratin were expressed in most examples. There was, however, differential expression of chromogranin A in that few prolactin (PRL) and adenocorticotrophic hormone (ACTH) adenomas stained positively, whereas all other adenoma subtypes were reactive. The ACTH adenomas had a unique profile with positive staining for galanin, neurophysin, vasopressin, and ubiquitin. These results indicate that (1) pituitary adenomas do not express a single “generic” immunophenotype; (2) synaptophysin is the most reliable and best broad spectrum marker for pituitary adenomas; (3) the neuroendocrine granule marker chromogranin A is useful in the identification of null cell adenoma, a tumor that usually does not stain for anterior pituitary tumors; and (4) among pituitary tumors, ACTH adenomas have a unique immunoprofile.     

Vitamin D and its analog EB1089 induce p27 accumulation and diminish association of p27 with Skp2 independent of PTEN in pituitary corticotroph cells

Disruption of the gene for the cyclin dependent kinase inhibitor (CDKI) p27/kip1 results in pituitary corticotroph hyperplasia while diminished expression of this protein has been described in aggressive human pituitary tumors. We have previously shown that 1,25-vitamin D3 (VD) hypophosphorylates p27 and interferes with the degradation of this CDKI in thyroid carcinoma cells. In this study we investigated whether VD/EB1089 can induce p27 accumulation and cause growth arrest of pituitary corticotroph cells. VD and EB1089 exhibited a significant reduction in AtT20 corticotroph but not PRL235 lactotroph cell growth. These changes were accompanied by selective accumulation of p27 in AtT20 but not in PRL235 cells. As p27 levels are highly dependent on protein degradation, we examined the effect of VD/EB1089 on p27 association with factors that target this CDKI to the proteasome. VD/EB1089 significantly restricted the association of p27 with Skp2 as well as with cyclin dependent kinase 2 (CDK2). As the tumor suppressor and phosphatase PTEN has been implicated in p27 regulation, we tested whether the effects of VD/EB1089 on p27 accumulation in corticotrophs could be mediated through this pathway. VD/EB1089 did not appreciably alter PTEN expression. Moreover, transfection of PTEN did not influence the effect of VD on p27 accumulation in corticotrophs. We conclude that VD/EB1089 can selectively arrest pituitary corticotroph growth and induce p27 accumulation.This effect is mediated at least partially through diminished p27 association with Skp2 and with CDK2. In contrast to other cell systems, PTEN does not participate in the regulation of corticotroph p27 and is not involved in mediating the effect of VD on p27 in these cells. Our findings highlight p27 and VD analogs as targets for manipulation and drug development respectively in the treatment of inoperable corticotroph adenomas.     

Human corticotroph cell adenomas

Sixty-one pituitary corticotroph adenomas from 47 patients with Cushing's disease, 10 with Nelson's syndrome, and four eucorticoid patients were studied by light microscopy, immunoperoxidase, and electron microscopy. Seventy nine percent of all tumors and 70% of Nelson's cases were microadenomas, sometimes minute. A contiguity between the posterior lobe and the adenoma was seen in ten cases. Spontaneous infarction of the tumor with remission of Cushing's syndrome occurred in one case. Light microscopy revealed that the adenoma cells were basophilic and contained PAS-positive granules also staining with Herlant tetrachrome and lead-hematoxylin. The granules stained positively with antiserum to adrenocorticotrophic hormone (ACTH), beta-lipotropic hormones (beta-LPH) and beta-endorphin. The most characteristic ultrastructural finding was the presence of perinuclear bundles of microfilaments found in all our cases. Oncocytic changes were seen in three tumors. Four silent corticotroph adenomas, two of them originally microadenomas that had enlarged to enclosed adenomas while being treated with bromocriptine for hyperprolactinemia and one a large diffuse invasive tumor, did not differ in their microscopic, immunocytological, or ultrastructural features.     

Monoclonal antibody HISL-19 as an immunocytochemical probe for neuroendocrine differentiation. Its application in diagnostic pathology.

The monoclonal islet cell antibody HISL-19 was generated after immunization of BALB/c mice with human islet cell preparations. Besides reactivity with all cells of the human pancreatic islet, MAb HISL-19 also reacted with other cells of the diffuse neuroendocrine system, including anterior pituitary cells, C cells of the thyroid, endocrine cells of the gut and bronchus, the adrenal medulla, and central and peripheral neurons. In this study the authors screened a series of 53 neuroendocrine and 71 nonneuroendocrine tumors for their reactivity with MAb HISL-19 using an indirect immunoperoxidase technique on formalin-fixed and Paraplast-embedded sections. MAb HISL-19 reacted strongly with all insulomas (10), carcinoids (8), C-cell carcinomas of the thyroid (8), pituitary adenomas (6), neuroendocrine carcinomas of the skin (4), paragangliomas of the carotid body (3), and pheochromocytomas (2) tested. Neuroblastomas (3), oat-cell carcinomas of the lung (2), and melanomas (4) exhibited only very few immunoreactive cells scattered throughout the tumor or remained unstained with MAb HISL-19. With the exception of one lobular carcinoma of the breast (1/3), one adenocarcinoma of the endometrium (1/4), and one adenocarcinoma of the stomach (1/6), nonneuroendocrine tumors were negative with MAb HISL-19. Biochemical findings obtained by SDS-PAGE, "Western" immunoblotting, immunoaffinity chromatography, and absorption experiments indicate that the MAb HISL-19-defined antigen is not related to neuron specific enolase. Because the epitope recognized by MAb HISL-19 is well preserved in formalin-fixed and routinely processed tissues, this monoclonal antibody finds potential applications in diagnostic pathology as an indicator for neuroendocrine cells and their neoplasms.     

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 corticotroph adenoma with crooke’s hyalinization

The diagnosis of pituitary corticotroph adenoma relies on the demonstration of a loss of the normal feedback control of adrenocorticotropic hormone (ACTH) biosynthesis by cortisol. The marked variability in the degree of ACTH suppression by glucocorticoids in these tumors, however, greatly enhances the difficulty in distinguishing Cushing’s disease from other syndromes of glucocorticoid excess. To illustrate this variability, we describe the clinical, biochemical, and morphological characteristics of a pituitary corticotroph adenoma in a 63-year-old woman, who presented with symptoms of a sellar mass but did not initially have florid Cushing’s disease. Light and electron microscopy of the pituitary tumor showed a corticotroph adenoma with Crooke’s hyalinization of the tumor cells, characterized by the accumulation of keratin immunoreactive microfilaments similar to those observed in normal corticotrophs in the presence of excess glucocorticoids. This case illustrates an unusual clinical presentation that may be associated with pituitary corticotroph adenoma showing Crooke’s hyalinization.     

Vesicular monoamine transporter 2 as a marker of gastric enterochromaffin-like cell tumors

The vesicular monoamine transporter 2 (VMAT2) facilitates the ATP-dependent accumulation of biogenic amine inside the secretory granules of endocrine cells and neurons and was demonstrated in the histamine-producing enterochromaffin-like (ECL) cells of the stomach. In the present investigation, VMAT2 immunohistochemistry was tested in 85 endocrine tumors, of which 60 were well differentiated gastrointestinal and pancreatic growths, 5 poorly differentiated (neuro)endocrine carcinomas (PDEC) and 1 mixed PDEC/ECL cell carcinoma of the stomach, 12 pheochromocytomas/paragangliomas, 3 adrenocortical lesions, 2 parathyroid and 2 lung neuroendocrine tumors. Extensive and intense VMAT2 immunoreactivity was observed in 16 of 16 gastric ECL cell tumors, 6 of 6 adrenal pheochromocytomas, 2 of 2 chromaffin paragangliomas and in 3 of the 4 carotid body paragangliomas investigated. Rare VMAT2-positive cells were observed in 12 of 21 intestinal enterochromaffin (EC) cell tumors, in 9 of 11 pancreatic neuroendocrine tumors, and in the mixed PDEC/ ECL cell carcinoma of the stomach (differentiated cells only). No VMAT2 immunoreactivity was observed in five gastrin, four somatostatin and three enteroglucagon/peptideYY tumors of the gastrointestinal tract, in six gastric PDECs, in three adrenocortical growths, and two parathyroid and two lung neuroendocrine tumors. These data support VMAT2 immunohistochemistry as being a useful tool for the diagnosis of gastric ECL cell tumors, separating them from all other endocrine tumors arising in the gastroduodenal area i.e., gastrin, somatostatin, EC cell and PDEC tumors, all of which proved essentially negative. Received: 28 June 1999 / Accepted: 20 October 1999     

Vasoactive intestinal peptide in the human pituitary gland and adenomas. An immunocytochemical study

Recent evidence indicates that vasoactive intestinal peptide (VIP) may be involved in normal pituitary function. Immunocytochemistry was used to localize VIP in human biopsied pituitary adenomas and postmortem anterior pituitary glands. Paraffin sections were immunostained for VIP with the avidin-biotin-peroxidase technique. Strong VIP-like immunoreactivity (VIP-LI) was observed in 16 of 17 prolactinomas, 12 of 14 growth hormone-secreting tumors associated with acromegaly, four of 12 ACTH-secreting tumors, and 14 of 18 nonfunctioning pituitary adenomas. In most cases, VIP was colocalized with the classical pituitary hormones. Six of the 18 nonfunctioning tumors had no demonstrable hormone immunoreactivity; five of these stained strongly for VIP, whereas one was negative. Of 18 normal anterior pituitaries, 12 showed strong diffuse staining for VIP throughout the gland. One pituitary with VIP-LI came from an individual who had undergone pituitary stalk transection. Double-immunoenzyme labeling and immunoelectron microscopy demonstrated VIP-LI in many lactotrophs, scattered thyrotrophs, corticotrophs, and in an occasional gonadotroph. These results suggest the following: 1) VIP is present in more than one cell type in normal and adenomatous human pituitaries; and 2) VIP may be involved in the function and development of pituitary tumors.