The role of calretinin, inhibin, melan-A, BCL-2, and C-kit in differentiating adrenal cortical and medullary tumors: an immunohistochemical study.

Morphologic distinction between adrenal cortical and medullary tumors can be difficult. Previous studies have shown inhibin, melan-A, and BCL-2 to be useful markers for adrenal cortical tumors. We have recently observed a high level of calretinin expression in normal adrenal cortex but not the medulla and therefore evaluated its diagnostic application for adrenal tumors in comparison with inhibin, melan-A, and BCL-2. C-kit is a transmembrane tyrosine kinase receptor. Immunodetection of c-kit expression has been recently used for tumor diagnosis, and c-kit-positive tumors can potentially benefit from kit kinase inhibitor treatment. Although c-kit expression was reported in adrenal medulla and pheochromocytoma, it has not been evaluated in adrenal cortical tumors. In this study, 28 adrenal cortical tumors (12 carcinomas, 16 adenomas), 20 pheochromocytomas, and 20 extraadrenal paragangliomas were evaluated for calretinin, inhibin, melan-A, BCL-2, and c-kit expression by standard immunohistochemical assays on paraffin sections. The percentage of immunoreactivity in adrenal cortical tumors was as follows: calretinin, 96%; melan-A, 89%; inhibin, 92%; BCL-2, 20%; and c-kit, 5%. Normal adrenal medulla did not stain for c-kit but was positive for BCL-2. Eighty-six percent of pheochromocytomas stained for BCL-2 and none for calretinin, with the exception of the ganglioneuromatous areas in composite pheochromocytomas (n = 5). Extraadrenal paragangliomas showed reactivity with calretinin in 25%, melan-A in 5%, inhibin in 16%, BCL-2 in 38%, and c-kit in 8% of the cases. Our results indicate that calretinin is the most sensitive among all the adrenal markers tested. Like melan-A and inhibin, calretinin is also a very specific marker in differentiating cortical from medullary adrenal tumors. In addition, calretinin can be used to confirm a composite pheochromocytoma. BCL-2 does not appear to be useful in differentiating adrenal cortical from medullary tumors. C-kit is not useful in the diagnosis of adrenal tumors, and kit kinase inhibitor might have a limited role in the treatment of adrenal tumors and paraganglioma because of the low frequency of c-kit expression in these tumors.     

A103 immunostaining in the diagnosis of adrenal cortical tumors: an immunohistochemical study of 316 cases

CONTEXT: The monoclonal antibody A103 recognizes an antigen on melanoma cells known as Melan-A or MART-1. Recent studies have shown that A103 also reacts with adrenal cortical cells and may be useful in the diagnosis of adrenal cortical tumors. However, only small numbers of some of the tumors in the differential diagnosis of adrenal cortical neoplasms have been studied. OBJECTIVE: To study the specificity of A103 immunohistochemistry in a large number of tumors in the differential diagnosis of adrenal cortical neoplasms. DESIGN: Formalin-fixed, paraffin-embedded tissue from 21 adrenal cortical tumors, 16 cases of metastatic carcinoma to the adrenal, 10 pheochromocytomas, and 269 extra-adrenal carcinomas was evaluated for A103 immunoreactivity using a commercially available antibody (Novocastra, Newcastle, UK). RESULTS: Positive staining was seen in all of the adrenal cortical tumors but in none of the adrenal metastases or pheochromocytomas. In the 269 extra-adrenal carcinomas, A103 immunoreactivity was limited to a single ovarian serous carcinoma. CONCLUSION: A103 immunostaining is useful in distinguishing adrenal cortical neoplasms from other carcinomas and pheochromocytoma.     

VEGF in 105 pheochromocytomas: enhanced expression correlates with malignant outcome

Pheochromocytomas are rare sympathoadrenal tumors that are highly vascular. Their malignancy is extremely difficult to estimate on the basis of histopathological features. Vascular endothelial growth factor (VEGF) is one of the most important angiogenic factors involved in both tumor growth and metastasis. In our search for new prognostic markers, we investigated the expression of VEGF in normal adrenal gland, in 105 primary pheochromocytomas, and in 6 metastases by using immunohistochemistry and Northern blot analysis. We also calculated the microvessel density of these tumors by staining the endothelial cells with monoclonal CD34 antibody. VEGF messenger ribonucleic acid was found in all pheochromocytomas studied. Immunohistochemically, VEGF was not found in normal adrenal medullary cells. Interestingly, all malignant pheochromocytomas (n=8), regardless of their primary location, had strong or moderate VEGF immunoreactivity, while most benign adrenal pheochromocytomas (26 of 37, 70.3%) were either negative or only weakly positive. The staining was heterogenous in extraadrenal pheochromocytomas as well as in a group of tumors that had histologically suspicious features but had not metastasized, here called borderline tumors (n=29). The microvessel density varied greatly in all of the tumor groups, and no statistical difference was found between these groups. Here we report moderate to strong VEGF expression in malignant pheochromocytomas, and negative or weak expression in benign adrenal pheochromocytomas. Normal medullary cells are immunohistochemically negative. Thus, low VEGF expression in pheochromocytomas favors a benign diagnosis.     

DLK is a novel immunohistochemical marker for adrenal gland tumors

Delta-like protein (DLK) is expressed in fetal and adult adrenal glands. We have investigated if this expression is maintained in adrenal gland-derived tumors. All the studied 37 cortical tumors, including five carcinomas, stained positively as well as the 13 examined pheochromocytomas. Thus, DLK is a very sensitive marker for adrenal tumors of cortical and medullary origin. Renal cell carcinomas, presenting the major differential diagnostic problem for cortical tumors, were all negative, as well as melanomas, which are similar to high portion of adrenocortical tumors that react with melan-A. However, all paragangliomas, some carcinoids, and thyroid medullary carcinomas were also positive for DLK. Therefore, this novel immunohistochemical marker seems useful for the identification of adrenocortical tumors while it has limited value for the distinction of pheochromocytomas from diagnostically related neuroendocrine tumors.     

Immunofluorescence microscopic evaluation of the intermediate filament expression of the adrenal cortex and medulla and their tumors.

Normal adrenal glands (10 specimens) and adrenal gland tumors (58 cases) were immunohistochemically evaluated for different types of intermediate filament (IF) proteins. Some of the normal cortical cells showed cytokeratin positivity, and no positivity was seen for epidermal keratin or other types of IF. In the adrenal medulla, neurofilament positivity was seen in nerve axons, some ganglion cells, and chromaffin cells; and cytokeratin-positive cells could not be detected. Only the vascular and connective tissue elements showed vimentin positivity in both cortical and medullary areas. In half of the cortical carcinomas (13/25), cytokeratin-positive tumor cells were found. Furthermore, vimentin-positive tumor cells were present in 10 of 25 cases, in some of them together with cytokeratin-positive cells. Thus, the results show heterogeneity among the adrenal cortical carcinomas. Interestingly, many benign adrenal cortical tissues and some carcinomas lacked immunoreactivity for all types of IF, suggesting a poorly developed IF system in these tissues. In contrast to adrenal cortical tumors, pheochromocytomas contained neurofilamentlike immunoreactivity. These results reflect the different cellular nature of adrenal cortical and medullary tumors, which apparently can be distinguished from each other with antibodies to intermediate filament proteins.     

Catecholamine-synthesizing enzymes and chromogranin proteins in drug-induced proliferative lesions of the rat adrenal medulla.

Both epinephrine (E) and norepinephrine (NE) cells in the rat adrenal medulla are able to proliferate in response to pharmacologic stimulation. However, previous biochemical studies have suggested that drug-induced or spontaneous pheochromocytomas in rats are almost invariably NE-producing. To resolve these apparently conflicting data, immunocytochemical techniques were utilized to establish functional profiles of adrenal medullary lesions classified as pheochromocytoma or nodular hyperplasia in rats treated chronically with a phosphodiesterase inhibitor which induced pheochromocytomas. Sixteen of 17 pheochromocytomas and all hyperplastic nodules stained positively for tyrosine hydroxylase and dopamine beta-hydroxylase, consistent with an ability to produce NE. No lesion of either type stained for phenylethanolamine N-methyltransferase, consistent with an inability to produce epinephrine. Lesions of both types showed variable staining for chromogranin proteins. The findings indicate that qualitative functional differences cannot be used to discriminate hyperplastic nodules from small pheochromocytomas in rats. Some lesions currently classified as hyperplastic nodules might in fact be small pheochromocytomas. Others might represent diffuse hyperplasia within pre-existing islands of NE-cells in a background of hyperplastic epinephrine-cells.     

Immunohistochemical localization of chromostatin and pancreastatin,chromogranin A-Derived bioactive peptides,in normal and neoplastic neuroendocrine tissues

Despite the widespread distribution of chromogranin A (CgA) in neuroendocrine tissues, the biological function of CgA has not yet been elucidated. The primary amino acid sequence of CgA, elucidated by cDNA analysis, has been revealed to include several pairs of basic amino acid residues that are homologous to the bioactive peptides, such as pancreastatin (PST) and chromostatin (CST). Using antibodies for human PST and CST, the immunohistochemical localization of these peptides was investigated in neuroendocrine tissues, including human pituitary glands, pancreas, adrenal medulla, various types of neuroendocrine neoplasms (13 pheochromocytomas, 10 medullary thyroid carcinomas, 11 pancreatic endocrine tumors, and 19 carcinoid tumors), and the cell line QGP-1N derived from human somatostatin-producing pancreatic endocrine tumor. Variable immunoreactive intensities of PST and CST were seen, but both peptides were detectable in all neuroendocrine tissues and in most of the neoplasms. Immunoreactivity for both PST and CST was observed in 100 and 73%, respectively, of pancreatic endocrine tumors, all pheochromocytomas, and 80 and 40%, respectively, of medullary thyroid carcinomas, as well as all nonrectal carcinoid tumors. In rectal carcinoids, cells immunoreactive for PST and CST were sparse. The distribution of PST and CST was similar to that of CgA, and it is considered that these peptides are simultaneously processed from CgA, and may play roles in autocrine and paracrine regulation on various hormones in addition to their previously known functions.     

Ret protein expression in adrenal medullary hyperplasia and pheochromocytoma

Ret is a developmentally regulated tyrosine kinase involved in formation and maintenance of the nervous system. Ret mutations predisposing to pheochromocytomas and medullary thyroid carcinomas occur in multiple endocrine neoplasia (MEN) syndromes 2A and 2B. Biochemical studies have demonstrated overexpression of Ret mRNA and protein in pheochromocytomas compared to normal adrenal medulla. However, the cellular distribution of Ret in the normal human adrenal and in hyperplastic lesions that antecede pheochromocytomas are unclear. The present investigation was undertaken to resolve the histological distribution of Ret in the normal human adrenal, in pheochromocytomas evolving from adrenal medullary hyperplasia in MEN2A and in sporadic pheochromocytomas. Ret expression was studied by immunohistochemistry using both a polyclonal and a monoclonal antibody, with confirmation by immunoblotting of representative cases. Only occasional cells stained for Ret in the normal adrenal, consistent with the distribution in adult adrenals of other species. Heterogeneous, progressively increased Ret expression was observed during the evolution of pheochromocytomas. In both normal and neoplastic adrenal, the most intense immunoreactivity was observed in cells with neuron-like features. Our finding that Ret is not expressed at high levels in the early stages of disease suggests that elucidation of mechanisms that regulate Ret expression is required for understanding the pathobiology of MEN2A. The association of high-level Ret expression with neuronal morphology suggests that the variable overexpression of Ret in pheochromocytomas might in part be an epiphenomenon, reflecting the known phenotypic plasticity of these tumors.     

An immunohistochemical study of pheochromocytomas

Twenty -six adrenal pheochromocytomas and four normal adrenal medullae were studied immunohistochemically. These included four malignant tumors with proven metastases, six tumors in patients with neurofibromatosis, nine tumors in patients with multiple endocrine neoplasia type 2, and seven sporadic nonfamilial pheochromocytomas. Immunohistochemical localization of neuron-specific enolase (NSE) was seen in all tumors and in the four normal adrenals. Methionine enkephalin-like immunoreactivity was present in tumors from all four groups and in the normal adrenals. Corticotropinlike immunoreactivity was found focally in two normal adrenal medullae and in four benign pheochromocytomas. Our results indicated that NSE was present in all four major groups of pheochromocytomas, including benign and malignant tumors. This marker aided in distinguishing between adrenal cortical and medullary tumors in unusually difficult cases, since all normal adrenal cortex and adrenal cortical tumors had negative test results for NSE.     

Distribution of chromogranin and S100 protein in normal and abnormal adrenal medullary tissues

The distribution of chromogranin and S100 protein was studied in 30 adrenal pheochromocytomas and 19 normal adrenal medullary tissues. Immunostaining in the tumors was compared with staining in sections of histologically normal medullae. Chromogranin showed diffuse cytoplasmic staining in all chromaffin cells. Chromogranin staining was consistently more intense in normal medullae, while less intense staining was present in most tumors from all four groups. S100 protein was present in the cytoplasm and nuclei of sustentacular cells surrounding chromaffin cells and in nerve branches. Many S100 protein-positive cells were present in normal medullae, in the two hyperplastic medullae, and in pheochromocytomas from patients with multiple endocrine neoplasia, type 2. Very few sustentacular cells were present in the other pheochromocytomas. These results indicate that S100 staining may be helpful in separating pheochromocytomas in patients with multiple endocrine neoplasia, type 2 disease from benign and malignant sporadic tumors.     

CD44 expression in normal adrenal tissue and adrenal tumours.

BACKGROUND: CD44 is a cell surface glycoprotein found on many normal cells, mainly lymphoid and epithelial. Normal cells usually express standard CD44 (CD44-S), whereas malignant tumours may express CD44 variant isoforms (CD44-V). CD44 expression has been described for neural crest derivatives. Characterisation of differences in CD44 expression may help in the diagnosis and differentiation of distinct adrenal tumours. AIMS: To examine CD44 expression in different layers of cortical cortex, in adrenal medulla, and in adrenal tumours. METHODS: CD44-S and CD44-V6 expression were studied in 12 cases of adrenal cortical adenoma, 3 of adrenal cortical carcinoma, 10 of pheochromocytoma, and 4 normal adrenal glands. RESULTS: CD44-V6 staining showed cytoplasmic expression in normal adrenal cortex and in cortical adenomas and carcinomas. Pheochromocytomas also showed CD44-V6 expression but in 5 of the 10 cases it was sparse, focal, and sometimes perinuclear. Strong membranous staining for CD44-S was observed in normal adrenal medulla. Analysis of CD44-S expression revealed differences between cortical adrenal tumours and pheochromocytomas. Ten of 12 cortical adenomas and 2 of 3 cortical carcinoma cells showed weak to moderate cytoplasmic staining, but all cases of pheochromocytoma had strong membranous staining. CONCLUSIONS: Membranous CD44-S staining may help to distinguish pheochromocytoma from adrenal cortical adenoma.     

Adrenocortical hemorrhagic necrosis: the role of catecholamines and retrograde medullary-cell embolism

We investigated the pathogenesis of adrenal necrosis using animal models of the disease (induced by administration of acrylonitrile, cysteamine, or pyrazole) and human cases. Results of electron-microscopic and histochemical time-response studies with rat models revealed an early, retrograde embolization of medullary cells and cell fragments in the cortical capillaries that showed prominent endothelial injury. The experimental adrenal lesions were prevented by surgical removal of the medulla one month before administration of adrenocorticolytic chemicals, or by the administration of the alpha-adrenergic antagonist phenoxybenzamine hydrochloride. Histochemical staining for medullary (argyrophil) granules in human cases of adrenal necrosis demonstrated tissue fragments that stained positively for silver in vascular cortical spaces in nine of ten autopsy specimens and in all four surgical cases we reviewed. Thus, catecholamines released from the adrenal medulla and from the retrograde medullary emboli in the cortex may have a role in the pathogenesis of adrenocortical necrosis.     

Adrenocortical carcinoma: diagnosis by fine needle aspiration cytology

Two cases of adrenal cortical carcinoma are described, wherein the diagnosis was established by fine needle aspiration cytology (FNAC). FNAC is increasingly being accepted as a means of diagnosis of adrenal cortical carcinomas. In yester years the diagnosis was established largely on post-operative histopathology. Adrenal cortical carcinomas are rare and account for less than 0.05% of all malignant neoplasms. Adrenal gland has become frequent target of needle biopsies with the availability of sensitive imaging techniques and better localization. Currently, needle biopsy is the only non-surgical means of obtaining a diagnosis in patient with adrenal mass. We present two cases of adrenal cortical carcinoma diagnosed on fine needle aspiration cytology (FNAC).     

Update on adrenal cortical neoplasia

The adrenal cortex gives rise to a biologically heterogenous group of neoplasms, each with a distinct morphology, antigen expression and molecular profile. Adrenal cortical adenomas have excellent prognosis and are usually cured by surgical resection alone, while adrenal cortical carcinomas are very aggressive tumors with a poor prognosis regardless of therapy. These tumors are rare and often challenging for a pathologist to diagnose, as significant overlap exists between benign and malignant lesions in some cases. In this review, we attempt to summarize most important histologic and clinical features of adrenal cortical adenomas and carcinomas, clarify the use of different grading systems, the use of special stains and the differential diagnosis for practicing pathologists. Most relevant hereditary syndromes associated with adrenal cortical tumors are listed. Updates in molecular alterations in adrenal cortical neoplasms and hyperplastic diseases as well as their clinical significance and potential therapeutic implications are also discussed.     

Fine-needle aspiration cytology of the adrenal gland. Fifty biopsies in 48 patients.

Fine-needle aspiration biopsy of 50 adrenal masses from 48 patients was performed between 1984 and 1991. The series consisted of 28 males and 20 females, with an age range of 12 months to 79 years (mean age, 55 years). Clinical and/or pathologic follow-up was available in 37 patients. Fine-needle aspiration was diagnostic in all 29 malignant cases having follow-up, with no false-positive diagnoses. There were six primary malignancies (three neuroblastomas, two pheochromocytomas, and one adrenal cortical carcinoma) and 23 metastatic lesions. Of these, the lung was the most frequent primary malignancy (60%), followed by melanoma and renal cell carcinoma (8.6% each). The remaining nonmalignant fine-needle aspiration diagnoses were adrenal cortical neoplasms (most likely adenoma), adrenal cortical hyperplasia, myelolipoma, benign adrenal tissue, and abscess. Based on clinical follow-up, three other adrenal adenomas were not diagnosed by fine-needle aspiration. Six biopsy specimens (12%) were insufficient for diagnosis. Ancillary studies including electron microscopy and/or immunocytochemistry were performed on 13 malignant aspirates and provided additional confirmation of the cytology diagnosis in 12 cases. This study confirms that fine-needle aspiration is a sensitive and highly specific procedure for the evaluation of primary and metastatic malignancies involving the adrenal gland. The technique is less useful in the workup of benign processes but, in some instances, can provide specific diagnostic information.     

Adrenal lymphangioma: clinicopathologic and immunohistochemical characteristics of a rare lesion

Adrenal lymphangiomas, also known as cystic adrenal lymphangiomas, are rare, benign vascular lesions that usually remain asymptomatic throughout life. Although previously adrenal lymphangioma lesions were primarily found at autopsy, they are currently detected during imaging work-up for unrelated causes and are likely to imitate other adrenocortical or adrenal medullary neoplasms. We aimed to retrospectively review all adrenal lymphangioma cases at our hospital and further document their lymphatic origin by immunohistochemical staining. A search of surgical pathology records (1984-2008) was conducted. All hematoxylin and eosin sections were retrieved from archives and reviewed by 2 pathologists in the study. Clinical information was gathered from electronic medical records. Representative paraffin-embedded sections from each case were selected for immunohistochemical analysis using monoclonal antibodies D2-40 and AE1/AE3. A total of 9 adrenal lymphangioma cases were identified (6 women and 3 men). All 9 patients were adults at time of diagnosis with a mean age of 42 years (range, 28-56 years). There were 7 white patients, 1 African American patient, and 1 Asian patient. The average size of an adrenal lymphangioma lesion was 4.9 cm (range, 2.0-13.5 cm). Adrenal lymphangioma was twice more frequently located on the right side (6 right-sided and 3 left-sided). Clinically, 4 (44%) of the 9 lesions presented with abdominal, flank, or back pain. One lymphangioma was found during work-up for labile hypertension. The remaining 4 lesions (44%) were asymptomatic and incidentally found during imaging studies for unrelated causes. Surgical removal was achieved by total adrenalectomy in 8 of the 9 lesions and by partial adrenalectomy in the remaining case. No evidence of recurrence or development of a contralateral lesion was encountered in any of the patients. Histologically, our adrenal lymphangiomas showed a typical multicystic architecture with dilated spaces lined by flattened, bland, simple lining. The cystic channels/spaces occasionally contained proteinaceous material and lacked red blood cell content. On immunohistochemical stains, D2-40 cytoplasmic staining was positive in all 9 examined lesions, whereas AE1/AE3 was negative, thus, confirming their lymphatic nature. D2-40 staining was diffuse in 2 and focal in the 7 remaining lesions. Adrenal lymphangiomas are very rare, benign lymphatic neoplasms with a female, right-sided predominance in our current series. They may clinically present with abdominal pain or can be incidentally found during adulthood as a mass, necessitating surgical removal to rule out other types of adrenal neoplasms.     

肾上腺髓质内、外嗜铬细胞瘤181例与多发性内分泌肿瘤的临床病理资料分析

目的 分析肾上腺髓质内、外嗜铬细胞瘤与多发性内分泌肿瘤2型( MEN2)的发病变化,探讨它们在临床症状、体征、病理变化方面的异同点和相互关系.方法 运用游程检验、方差分析、t检验、x2检验,对天津医科大学总医院病理科1993-2008年181例肾上腺髓质内、外嗜铬细胞瘤(根据世界卫生组织《内分泌器官肿瘤病理学和遗传学2004年版》分别将其分为良性、恶性倾向、恶性病变3组)及伴MEN2的检出率、构成比、平均诊断年龄、性别比例及临床表现、病理变化进行统计学分析.结果 16年外检总数167 702例,肾上腺疾病、肾上腺髓质内、外嗜铬细胞瘤的例数(外检率)分别是910例(0.54％)、139例(0.08％)、42例(0.03％),其中嗜铬细胞瘤的良性、恶性倾向、恶性3组的例数(构成比)在肾上腺髓质内分别是102例(73.4％)、29例(20.9％)、8例(5.7％),102例良性病变中伴MEN2者共8例(7.8％);在肾上腺髓质外分别是18例(42.8％)、12例(28.6％)、12例(28.6％).16年间肾上腺疾病、肾上腺髓质内、外嗜铬细胞瘤及良性病变伴MEN2的检出率和构成比及嗜铬细胞瘤的良性、恶性倾向、恶性3组的构成比均无变化趋势(P＞0.05),并随病变恶性度的增加逐渐由女性多见转变为男性多见的发病规律.嗜铬细胞瘤患者总平均诊断年龄在髓质内良性组、恶性倾向组分别为42.7和40.1岁,均低于恶性组患者的51.6岁.髓质外良性组、恶性倾向组分别为43.1和45.2岁,均高于恶性组的37.8岁(P＜0.05).恶性病变患者中,髓质内的发病年龄(51.6岁)明显高于髓质外(37.8岁,P＜0.05);伴MEN2患者只见于患肾上腺髓质内良性嗜铬细胞瘤的女性,其平均诊断年龄(38.9岁)低于良性病变(42.7岁),而且甲状腺髓样癌的发生均早于肾上腺髓质内嗜铬细胞瘤.肾上腺髓质内、外嗜铬细胞瘤患者均显示恶性病变伴有高血压症状者的比例较良性、恶性倾向者明显下降(P＜0.05).仅肾上腺髓质内嗜铬细胞瘤发生双侧病变,其中恶性病变( 2/8)的发生率明显高于良性(15.7％)、恶性倾向(6.9％).复发病变在肾上腺髓质内、外嗜铬细胞瘤的比例均随良性(11.8％,0)、恶性倾向(13.8％,25％)、恶性(33.3％,37.5％)的病变恶性度的上升而逐渐增加.肾上腺髓质内、外嗜铬细胞瘤体积平均直径亦随良性(4.2、4.0 cm)、恶性倾向(5.3、5.6 cm)、恶性病变(7.3、6.9 cm)的恶性度上升而逐渐增大(P＜0.05).结论 肾上腺髓质内、外嗜铬细胞瘤良性、恶性倾向、恶性病变3组的临床表现与病理变化密切相关,确切的病变类型和肿瘤性质仍要由病理学检查确定.     

Immunohistochemical staining of normal, hyperplastic, and neoplastic adrenal cortex with a monoclonal antibody against alpha inhibin.

AIMS: To investigate the immunohisto-chemical staining of normal, hyperplastic, and neoplastic adrenal cortex with a monoclonal antibody against alpha inhibin. Also, to determine whether immunostaining with this antibody is useful in differentiating between adrenal cortical neoplasms and other tumours involving the adrenal gland that might mimic them. METHODS: Normal adrenal tissue (n = 20) and specimens from cases of adrenal hyperplasia (n = 13), adrenal cortical adenoma (n = 15), adrenal cortical carcinoma (n = 4), phaeochromocytoma (n = 8), and adrenal metastatic tumour (n = 7) were stained with a monoclonal antibody against the alpha subunit of human inhibin. RESULTS: Positive staining with the anti-alpha inhibin monoclonal antibody was seen in all normal adrenal glands. Immunoreactivity was largely confined to the inner cell layers of the adrenal cortex, with no staining of the adrenal medulla. All hyperplastic adrenal glands and adrenal cortical adenomas and carcinomas were also immunoreactive. The other tumours studied were negative. CONCLUSIONS: There is consistent immunoreactivity with the anti-alpha inhibin monoclonal antibody in normal adrenal cortex and in hyperplastic and neoplastic adrenal cortical lesions. In the normal adrenal cortex, positive staining is mainly confined to the zona reticularis. Other neoplasms involving the adrenal gland are negative. Immunohistochemical staining with anti-alpha inhibin monoclonal antibody, performed as part of a panel, may prove to be of value in the distinction between adrenal cortical carcinoma and phaeochromocytoma or metastatic tumour.     

Monoclonal Antibodies Recognizing Normal and Neoplastic Human Adrenal Cortex

Four monoclonal antibodies (MAb) were generated by immunization of mice with dispersed cells from normal human adrenal gland (Na) and adrenocortical adenoma causing cortisol excess (Ac). Immunohistochemically reacted cryosections revealed differential labeling of the normal cortical parenchyma, and immunofluorescence on dispersed cells displayed that Ac5 alone labeled the cell surface. Immunoprecipitation demonstrated that the antibodies recognized apparently different structures of 51-88 kDa. Immunohistochemical examination of several normal human tissues substantiated restricted reactivity, especially for the Na2 and Na7 antibodies, and that the adrenal medulla was not stained by any of the antibodies. The antibodies recognized the vast majority of the parenchymal cells of cortical adenomas (n = 21). Each antibody also reacted with all adrenocortical carcinomas (n = 17), and the staining generally was most intense and extensive with Na7. Analysis of other pathological human tissues revealed highly restricted reactivity for the Na2 antibody. Na2 and Na5 failed to stain 17 renal cell carcinomas. None of the antibodies recognized pheochromocytomas. These antibodies may lead to improved histological recognition and characterization of human adrenal lesions.     

Up-regulation of ret by reserpine in the adult rat adrenal medulla

The receptor tyrosine kinase, ret, is activated by glial cell line-derived neurotrophic factor, neurturin and related ligands that bind to glycosylphosphatidylinositol-tailed receptors GFRalpha1-4. Ret expression is developmentally regulated and detectable only at very low levels in adult adrenal medulla. However, mutations of ret that cause constitutive activation or alter signal transduction give rise to adrenal medullary hyperplasia and pheochromocytomas in humans with hereditary multiple endocrine neoplasia (MEN) syndromes 2A and 2B and in animal models. These discordant observations pose the conundrum of how a molecule barely detectable in the adult adrenal can contribute to development of adrenal medullary pathology that typically occurs in adults. We recently reported that depolarization and phorbol esters that activate protein kinase C act synergistically with neurturin to up-regulate ret protein and mRNA expression in adult rat chromaffin cell cultures. Those findings suggested that ret expression in vivo is not static and might be regulated in part by neurally derived signals. We show here that the anti-hypertensive agent reserpine, which is known to cause a reflex increase in trans-synaptic stimulation of chromaffin cells, increases expression of ret mRNA and protein in adult rat adrenal medullary tissue in vivo. Elevated ret protein levels are detectable both by immunoblots and immunohistochemistry, which shows immunoreactive ret in chromaffin cells and neurons after reserpine administration. The finding that ret expression is subject to up-regulation by environmental signals in vivo suggests that epigenetic factors might influence the development of adrenal medullary disease by affecting the expression of ret. It is known that long-term administration of reserpine leads to the development of adrenal medullary hyperplasia and pheochromocytomas in rats. Our findings suggest potential utility of the rat model for studying the roles of ret in the adrenal medulla and the mechanisms of its involvement in MEN 2 and other pheochromocytoma syndromes.