Rapidly recurring folliculostellate cell tumor of the adenohypophysis with the morphology of a spindle cell oncocytoma: case report with electron microscopic studies.

We report a rapidly recurring folliculostellate cell tumor of the adenohypophysis in a 63-year-old woman. Morphologically the tumor had the typical appearance of a spindle cell oncocytoma of the adenohypophysis. It recurred within 5 months of selective transsphenoidal resection, requiring a second transsphenoidal operation followed by radiation therapy. The spindle cell oncocytoma (SCO) of the adenohypophysis is a relatively recently described entity and a new addition to the fourth edition of the WHO Classification of Tumors of the Central Nervous System. In our case, the ultrastructural features were significantly different from those so far described in SCO, in that tumor cells formed a network of structures indistinguishable from pituitary follicles. In addition, a minority of tumor cells exhibited endocrine differentiation.

Silent adenoma subtype 3 of the pituitary--immunohistochemical and ultrastructural classification: a review of 29 cases.

The silent adenoma subtype 3 (SAS-3) of undetermined cellular derivation is a seemingly nonfunctioning aggressive pituitary tumor with a high recurrence rate. At the time of diagnosis SAS-3s are macro- or giant adenomas particularly aggressive in young individuals, especially women. They are usually associated with mild hyperprolactinemia and are unremarkable by histology. Immunohistochemistry, demonstrating scattered immunoreactivity mostly for GH, PRL, TSH, and alpha-subunit, is not diagnostic. Presently, only TEM permits conclusive diagnosis. Ultrastructurally, the large polar adenoma cells contain abundant RER, masses of SER, extensive multipolar Golgi apparatus, and unevenly clustered mitochondria, displaced by RER and SER, which may show close spatial relationship to RER. Cell membranes often form plexiform interdigitations. Nuclear pleomorphism and nuclear inclusions are common. The 100- to 200-nm secretory granules accumulate heavily in cell processes, which is a hallmark of glycoprotein hormone cell differentiation. The endothelial cells may contain tubuloreticular inclusions. Complete surgical removal of the large often invasive tumors is difficult necessitating postoperative treatment. SAS-3 is sensitive to conventional radiation. Some tumors express somatostatin receptors and respond well to somatostatin analogues, offering long-term control in patients with residual tumor. Possible derivation of SAS-3 from rostral thyrotrophs, a cell type presently known in rodents is contemplated.

Distinct clonal composition of primary and metastatic adrencorticotrophic hormone-producing pituitary carcinoma.

The pathogenetic mechanisms underlying pituitary tumorigenesis are largely unknown. Previous reports have suggested that aggressive pituitary adenomas and/or carcinomas may be associated with genetic alterations that are distinct from those responsible for the more common and less aggressive pituitary adenomas. Here, we describe the clonal composition of a pituitary carcinoma, its recurrence and its metastasis. The samples studied were from a 48-year-old woman who presented with recurrent Cushing's syndrome. During the 8-year course of her disease, she had an ACTH-producing pituitary carcinoma requiring two transsphenoidal procedures and resection of a metastatic cervical lymph node. Her disease remained active despite surgical resection, external beam irradiation and medical treatment with ketoconazole. Ultimately, bilateral adrenalectomy was performed to control the hypercortisolism. Morphological and immunohistochemical studies revealed that the primary and recurrent pituitary tumours and the metastatic lesion were an endocrine tumour with ACTH and growth hormone immunoreactivity. Primary, recurrent and metastatic tumour DNAs were analysed for X-chromosome inactivation and loss of heterozygosity (LOH) at several microsatellite loci on chromosomes 9,10, 11, 13 and 22. All three lesions were monoclonal in composition as suggested by the pattern of X chromosome inactivation of the PGK-1 allele. Moreover, the primary, recurrent and metastatic lesions demonstrated LOH at the microsatellite allelic markers PYGM and D10S217. In contrast, however, the metastatic lesion showed a loss-to-retention pattern at two distinct loci (IFNA and D22S156) compared to the primary and recurrent pituitary tumours. These findings, while consistent with a clonal composition of the primary and metastatic pituitary lesions, show each clone to be distinct. This is the first description of a metastatic pituitary carcinoma with a distinct clonal composition from its primary source.

Severe lymphocytic adenohypophysitis with selective disappearance of prolactin cells: a histologic, ultrastructural and immunoelectron microscopic study.

We report the first documented example (case 1) of lymphocytic adenohypophysitis (LAH) associated with selective destruction of prolactin cells. The morphologic data are compared to those obtained in another, more typical case (case 2). Case 1 was a 35-year-old woman with remote history of pregnancy who presented with headache, oligomenorrhea and visual disturbances. The blood prolactin level was nearly undetectable, but no deficiency of other pituitary hormones was evident. A sellar and parasellar mass compressing the optic chiasm was removed transsphenoidally. Histology demonstrated massive infiltration with lymphocytes, plasma cells and macrophages causing marked destruction of pituitary acini. Part of the gland was fibrotic. Immunocytochemistry documented all pituitary hormones, but only few cells, probably mammosomatotrophs, were immunoreactive for prolactin. Electron microscopy and immunoelectron microscopy using double gold labeling for growth hormone and prolactin detected no prolactin cells. A striking ultrastructural finding was the prominence of folliculostellate cells in areas of active cell destruction supporting the presumed immune role of these cells. LAH in case 2 (24-year-old woman) became manifest during late pregnancy, causing pituitary enlargement and visual field defects. Pituitary tests showed no major hormonal deficits. Moderate hyperprolactinemia was appropriate for her pregnancy status. A sellar mass, thought to be adenoma, was removed. Histology demonstrated multifocal LAH without major destruction of acinar structures. Immunocytochemistry and electron microscopy documented all pituitary cell types including the marked abundance of prolactin-producing cells, resultant of gestational prolactin cell hyperplasia. In addition to prolactin cells and growth hormone cells, immunoelectron microscopy showed several bihormonal mammosomatotrophs, also appropriate for pregnancy.

Growth hormone-releasing hormone (GHRH) and GHRH receptor (GHRH-R) isoform expression in ectopic acromegaly.

Bronchial endocrine neoplasms causing acromegaly due to ectopic production of growth hormone (GH)-releasing hormone (GHRH) have been reported. We describe the case of a 39-year-old man with clinical and biochemical acromegaly. Magnetic resonance imaging revealed an enlarged pituitary, which was confirmed histologically to harbour somatotroph hyperplasia. Further investigations identified a circumscribed central mass in the right lung which was surgically resected and histologically confirmed to be an endocrine tumour with strong immunopositivity for GHRH, synaptophysin and chromogranin; the lesion also exhibited mild positivity for peptide YY, calcitonin gene-related peptide (CGRP), glucagon-like peptide (GLP)-1, corticotrophin-releasing hormone (CRH), tyrosine hydroxylase, vasoactive intestinal peptide (VIP) and enkephalin. S100 protein was identified in stellate cells surrounding nests of epithelial tumour cells. The MIB-1 antibody labelled about 10% of the tumour cells. We established that the tumour not only produced GHRH but the GHRH-receptor (GHRH-R) as well. GHRH and GHRH-R mRNA were identified and the latter was characterized as two variants, a full-length transcript and a truncated splice variant that has been described in human pituitary somatotroph adenomas. We suggest that GHRH expression by this tumour and the presence of its receptor may be responsible for enhanced growth. The expression of a truncated splice variant that is unable to transduce GHRH signalling may be implicated in the less aggressive behaviour of well-differentiated endocrine tumours that produce GHRH compared with small-cell lung carcinomas that are very responsive to GHRH growth stimulation.

The spectrum and significance of primary hypophysitis.

Hypophysitis can present clinically as a mass lesion of the sella turcica. Secondary hypophysitis occurs in cases where a definite etiologic agent or process inciting the inflammatory reaction can be identified. In contrast, primary hypophysitis refers to inflammation confined to the pituitary gland with no identifiable etiologic associations. We report three cases of primary hypophysitis to illustrate the spectrum of three clinicopathological entities that encompass this disease: lymphocytic hypophysitis, granulomatous hypophysitis, and xanthomatous hypophysitis. Our three patients underwent surgery, with variable response. However, conservative, supportive treatment with or without surgical decompression is generally favored over aggressive and extensive surgical resection that results in hypopituitarism. We conclude that the optimal management of patients with hyophysitis requires a high index of suspicion before extensive surgical resection. Histological confirmation of the diagnosis of hypophysitis can be obtained by performing a biopsy or by requesting an intraoperative frozen section consultation.

Reversible transdifferentiation: interconversion of somatotrophs and lactotrophs in pituitary hyperplasia.

Previous studies conclusively demonstrated transformation of somatotrophs into bihormonal mammosomatotrophs in gestational lactotroph hyperplasia during pregnancy. Similar transdifferentiation of somatotrophs into thyrotrophs through bihormonal intermediate thryrosomatotrophs was documented during thyrotroph hyperplasia in both rodent and human pituitaries in hypothyroidism. The cessation of the stimulation resulted in reversal of the process in both conditions. The conversion of lactotrophs into somatotrophs was suggested but not documented previously in the human gland. The present study was undertaken to investigate cases of somatotroph hyperplasia by transmission electron microscopy, immunoelectron microscopy using double immunogold labeling for growth hormone and prolactin, as well as combined immunocytochemistry and in situ hybridization. Adenohypophysial tissue was removed from a 38-year-old man and a 29-year-old woman with long-standing acromegaly due to ectopic overproduction of growth hormone-releasing hormone (GRH) by bronchial carcinoid tumors. For comparison, two pituitary biopsies were studied: one from a 38-year old woman with idiopathic lactotroph hyperplasia and one from a 14-year-old boy with secondary lactotroph hyperplasia due to a suprasellar craniopharyngioma. In the patients with somatotroph hyperplasia, the prevailing cell type was the hyperplastic somatotroph joined by mammosomatotroph deriving from lactotrophs, whereas monohormonal lactotrophs were rare. The predominance of mammosomatotrophs and active lactotrophs was documented in the patient with idiopathic lactotroph hyperplasia, whereas the case of the patient with secondary lactotroph hyperplasia was characterized by monohormonal lactotrophs and somatotrophs, but mammosomatotrophs were rare. That finding in the pituitary of the boy suggests that participation of mammosomatotrophs in lactotroph hyperplasia is not unconditional Our findings conclusively demonstrate conversion of lactotrophs into mammosomatotrophs during somatotroph hyperplasia, providing further evidence for the potential of reversible transdifferentiation between somatotrophs and lactotrophs in response to functional demand.

Cystic lesions of the pituitary: clinicopathological features distinguishing craniopharyngioma, Rathke's cleft cyst, and arachnoid cyst.

The distinction among craniopharyngioma (CR), Rathke's cleft cyst (RCC), and intrasellar arachnoid cyst (AC) remains a difficult preoperative problem. Accurate diagnosis of these rare pituitary lesions is important to determine the type of treatment and predict prognostic outcome. The majority of the literature describes the clinical manifestations and management of only one of CR, RCC, or AC, rendering comparisons difficult. We conducted a study to 1) investigate distinguishing preoperative clinical, biochemical, and radiographic features of patients with CR, RCC, and AC; and 2) identify clinicopathological features that independently predict recurrence in CR and RCC in adults. Fifty-two adult patients included 21 patients with CR (mean age at initial surgery, 35 +/- 14 yr), 26 patients with RCC (mean age, 37 +/- 14 yr), and 5 patients with AC (mean age, 53 +/- 12 yr). Mean follow-up duration was 70 +/- 13 months. Patients with CR presented with hypopituitarism in 95% of cases and hyperprolactinemia in 38%. These patients also had more preoperative neurological deficits (67%), ophthalmological complaints (67%), and significantly higher psychiatric manifestations (33%; P = 0.003) than those with RCC or AC. Patients with AC presented with headaches (60%), visual field deficits (60%), or impotence (50%) in the absence of other specific endocrine dysfunction symptoms. Using biochemical criteria, the percentage of patients with two or more pituitary hormonal axes impaired preoperatively was 67% for CR and 62% for RCC, significantly greater (P = 0.03) than that for the AC patients who had pituitary dysfunction of only one axis. The composition of CR lesions was cystic (38%), solid (10%), or mixed solid and cystic (43%). Patients with RCC or AC groups had a significantly greater proportion (P = 0.006) of purely cystic lesions (88% and 100%, respectively). Calcification detectable on computed tomographic scanning was present in 87% of patients with CR, a significantly greater proportion (P < 0.001) compared to those with RCC (13%) or AC (0%). No significant differences were found between the groups based on computed tomography density, the presence of postcontrast enhancement, or magnetic resonance imaging. Recurrence rate was 62% for CR, 19% for RCC, and 20% for AC. Surgical intervention statistically improved most neurological, ophthalmological, and psychiatric manifestations; in contrast, galactorrhea, menstrual dysfunction, and diabetes insipidus (52% CR; 31% RCC) did not improve or became worse postoperatively. A significantly higher percentage of patients with CR required postoperative hormone replacement. Similarly, there was a biochemical trend suggesting that a smaller proportion of patients with CR improved in at least one pituitary axis after surgery (P = 0.08) compared to those with RCC or AC. There was a positive correlation between cyst size and recurrence rate (r = 0.689; P < 0.01) and between cyst size and time to recurrence (r = 0.582; P = 0.037) for all three groups. We describe the largest clinical, biochemical, radiographic, and histological series of adult patients with cystic disease of the sella turcica. Patients with AC tended to be older at initial diagnosis than CR or RCC patients. Mass effects, such as visual problems and headaches, are common symptoms of all three cystic lesions, but psychiatric deficits favor a diagnosis of CR. Calcification or solid components on neuroimaging characterize CR. Endocrinological deficits, especially diabetes insipidus, had the worst prognosis after surgery. Low recurrence rates can be expected for RCC and AC. These data have direct implications for the management and monitoring of patients with cystic lesions of the sella turcica.

Clinicopathological variations in cushing's syndrome.

In the majority of cases, Cushing's disease is the result of a small basophilic corticotroph microadenoma with an average size of less than 5 mm. Transsphenoidal microsurgery can cure patients with Cushing's disease; however, selective removal of the lesion requires precise preoperative localization. In this article, we present the pathological findings and clinical outcomes of four patients who underwent inferior petrosal sinus sampling (IPSS) for ACTH, pituitary imaging and subsequent transsphenoidal surgery for the diagnosis and treatment of Cushing's disease. All patients fulfilled accepted biochemical criteria for the diagnosis of ACTH-dependent Cushing's syndrome. Histological examination revealed a basophilic corticotroph adenoma in two patients. In one other patient, only Crooke's hyalinization was found; however, the patient achieved a complete clinical and biochemical remission following a hemihypophysectomy based on IPSS findings. Thus, a microadenoma was assumed or proven in three patients, of whom two were cured by surgery alone. In the third patient, cortisol excess persisted following transsphenoidal surgery because of a coexistent functioning adrenal adenoma. The fourth patient developed recurrent nodular corticotroph hyperplasia following a 17-yr remission. The second transsphenoidal procedure failed to ameliorate cortisol excess, necessitating a subsequent bilateral adrenalectomy. IPSS accurately localized the site of the lesion in all four cases. Although magnetic resonance imaging (MRI) identified a distinct lesion in three cases, two of these represented false positives (a cyst in one case and a prolactinoma in the other), whereas in only one did MRI correctly match the site of the lesion. In each case, conflicting test results and/or difficult management decisions posed a challenge. Thus, successful resolution of disease requires a multidisciplinary approach to validate clinical, biochemical, and radiographic data based on morphologic findings.

Improved diagnostic accuracy of inferior petrosal sinus sampling over imaging for localizing pituitary pathology in patients with Cushing's disease.

The majority of patients with Cushing's disease can be cured by transsphenoidal microsurgery; however, precise localization of the pituitary source of ACTH is not always possible by standard imaging techniques. Bilateral venous sampling from the inferior petrosal sinuses (IPSS) is also useful for diagnosing Cushing's disease, but the interpretation of discordant findings between IPSS and imaging remains problematic. We tested the ability of imaging and IPSS to localize an ACTH-secreting pituitary lesion in comparison to definitive histopathological examination of the pituitary in patients with Cushing's disease (n = 37). Bilateral IPS catheterization was technically feasible in 32 patients and provided evidence of lateralization in 31 patients. Histological examination confirmed a corticotropic adenoma in 28 patients and corticotropic hyperplasia in 2 patients; Crooke's hyaline change was found in 7 patients, among whom 1 subsequently was found to have an ectopic sphenoid corticotropic adenoma, and the remainder had suspected microadenomas that were not identified microscopically. Accurate localization of the pituitary lesion was more frequent when based on IPSS results than on imaging studies (70% vs. 49%, P < 0.06). The 2 tests provided directly discrepant results for 8 patients; among these, IPSS was more likely than imaging to agree with final pathology (63% vs. 13%, P < 0.10). Imaging was entirely normal for another 9 patients, in whom IPSS accurately localized the lesion for the majority (89%; 95% confidence interval: 50-99%). We suggest that IPSS is an effective tool for localizing pituitary pathology and planning surgery for patients with Cushing's disease.

A composite silent corticotroph pituitary adenoma with interspersed adrenocortical cells: case report.

OBJECTIVE AND IMPORTANCE: A case report of an extraordinary sellar pituitary tumor composed of corticotrophs and adrenocortical cells is presented. To our knowledge, this is only the second one reported in the literature. CLINICAL PRESENTATION: An 18-year-old female patient presented with amenorrhea. INTERVENTION: Investigations revealed a sellar mass, which was excised transsphenoidally. Histologically, two cell types could be readily distinguished, i.e., small basophilic cells that were positive for periodic acid Schiff and adrenocorticotropic hormone and large cells with abundant, slightly vacuolated, eosinophilic cytoplasm that were negative for periodic acid Schiff and adrenocorticotropic hormone. The nature of the tumor was revealed by ultrastructural examination, thus highlighting the importance of this technique in the investigation of pituitary adenomas. Immunohistochemistry with a panel of steroidogenic dehydrogenases and hydroxylases was positive in the large cells, confirming these as adrenocortical cells. CONCLUSION: We suggest that the designation "composite silent corticotroph pituitary adenoma with adrenocortical cells" is an appropriate name for this tumor. The explanation for the presence of the two cell types is obscure. Two theories are considered, as were proposed by the authors of the previous case report regarding the same entity, i.e., 1) the possibility of misplaced embryonic adrenocortical cells and 2) the presence of uncommitted stem cells that differentiate into adrenocortical cells.

Overexpression of the growth-hormone-releasing hormone gene in acromegaly-associated pituitary tumors. An event associated with neoplastic progression and aggressive behavior.

The clinical behavior of growth hormone (GH)-producing pituitary tumors is known to vary greatly; however, the events underlying this variability remain poorly understood. Herein we demonstrate that tumor overexpression of the GH-releasing hormone (GHRH) gene is one prognostically informative event associated with the clinical aggressiveness of somatotroph pituitary tumors. Accumulation of GHRH mRNA transcripts was demonstrated in 91 of a consecutive series of 100 somatotroph tumors by in situ hybridization; these findings were corroborated by Northern analysis and reverse transcriptase polymerase chain reaction, and protein translation was confirmed by Western blotting. By comparison, transcript accumulation was absent or negligibly low in 30 normal pituitary glands. GHRH transcripts were found to preferentially accumulate among clinically aggressive tumors. Specifically, GHRH mRNA signal intensity was 1) linearly correlated with Ki-67 tumor growth fractions (r = 0.71; P < 0.001), 2) linearly correlated with preoperative serum GH levels (r = 0.56; p = 0.01), 3) higher among invasive tumors (P < 0.001), and 4) highest in those tumors in which post-operative remission was not achieved (P < 0.001). Using multivariate logistic regression, a model of postoperative remission likelihood was derived wherein remission was defined by the single criterion of suppressibility of GH levels to less than 2 ng/ml during an oral glucose tolerance test. In this outcome model, GHRH mRNA signal intensity proved to be the most important explanatory variable overall, eclipsing any and all conventional clinicopathological predictors as the single most significant predictor of postoperative remission; increases in GHRH mRNA signal were associated with marked declines in remission likelihood. The generalizability of this outcome model was further validated by the model's significant performance in predicting postoperative remission in a random sample of 30 somatotroph tumors treated at another institution. These data indicate that overexpression of GHRH gene is an event associated with the neoplastic progression and clinical aggressiveness of somatotroph adenomas. More generally, these data merge essential elements of the hypothalamic and pituitary hypotheses of pituitary tumorigenesis, providing for a more unified concept of neoplastic progression in the pituitary.

The c-erbB-2/neu proto-oncogene in human pituitary tumours.

OBJECTIVE: The aetiology of most pituitary tumours remains unknown. We have examined the potential role of neu receptor proto-oncogene in human pituitary tumorigenesis. MATERIALS AND METHODS: Ten non-tumorous pituitary glands and 16 morphologically characterized functional and clinically non-functioning pituitary adenomas were studied. Protein expression was examined by immunohistochemistry, mRNA expression by RT-PCR and competitive PCR, gene amplification by differential PCR, and point mutations by DNA sequencing. RESULTS: Cytoplasmic positivity for neu was identified in a few scattered cells of the non-tumorous adenohypophysis using an antibody to the intracytoplasmic domain of neu, but no membrane staining was found with an antibody to the extracellular domain; the latter is said to reflect gene amplification. mRNA transcript signals of the expected size were identified in the normal adenohypophysis and in all 16 adenomas examined. No increase in the degree of mRNA expression, however, was noted in the different tumour types compared to normal human pituitary tissue as determined by competitive PCR. As neu can be activated to an oncogene by a point mutation in the transmembrane region, nucleotide substitutions in this domain were investigated. Direct sequencing of codon 659 revealed no point mutations in any of the tumours. Furthermore, since amplification of neu has been noted in various human malignancies, DNA from these tumours was examined by differential PCR. No detectable differences were noted between the neu gene and the single-copy reference gene IFN-gamma. CONCLUSION: The neu gene is expressed in adenohypophysial cells and their tumours. In pituitary adenomas, this expression is not associated with gene amplification or activating mutations to suggest a direct role in pituitary tumorigenesis.

Cell-specific expression of estrogen receptor in the human pituitary and its adenomas.

Estrogen affects the synthesis and release of several pituitary hormones. The estrogen receptor (ER), a member of the steroid hormone receptor family, is thought to mediate transcriptional effects in a cell-specific fashion. We investigated whether ER is expressed in specific hormone-producing cell types in the human pituitary and its adenomas. Pituitary adenomas (n = 34) were collected at the time of surgery, and normal glands were obtained from autopsy. Expression of ER messenger ribonucleic acid (mRNA) was determined by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. ER was also localized with immunohistochemistry and protein extraction. By RT-PCR, ER mRNA was found in the nontumorous pituitary and in pituitary adenomas expressing only PRL, in those producing GH and PRL, and in adenomas expressing the gonadotropic hormones. No ER mRNA was detected in adenomas expressing only GH without PRL or gonadotropins, nor in tumors producing ACTH without PRL or gonadotropins. In situ hybridization was not as sensitive or specific as RT-PCR. Biochemical analysis performed on seven tumors that were positive for ER mRNA by RT-PCR detected ER protein in only one PRL adenoma and one oncocytoma and yielded negative or equivocal results in one PRL adenoma, three GH-PRL adenomas, and one null cell adenoma. ER protein was localized by immunohistochemistry in scattered cells of the nontumorous adenohypophysis and in a few PRL and gonadotroph adenomas. We conclude that ER expression, as determined by RT-PCR, correlates with the expression of PRL or gonadotropins; in contrast, ER mRNA was not detected in adenomas that express only GH or ACTH. These findings implicate ER as a cell-specific transcription factor that may regulate cytodifferentiation in the pituitary.

Asynchronous pituitary adenomas with differing morphology.

Recurrent pituitary tumors can sometimes pose a diagnostic and therapeutic challenge. We report a case of a 43-year-old man who presented twice, 13 years apart, with pituitary adenoma marked by headaches, visual impairment, and no signs of endocrinologic abnormality. At initial presentation computed tomographic scan documented a pituitary mass eroding the sellar floor, with suprasellar and parasellar extension. The patient underwent transsphenoidal surgery and the tumor was classified as a silent corticotroph adenoma, subtype 2. Thirteen years later, clinical symptoms of a destructive pituitary mass reappeared. This time, the adenoma revealed typical ultrastructural features of an oncocytoma; it had a different immunocytochemical profile from the first tumor. Given these striking morphologic differences, we consider the two adenomas to represent asynchronous, de novo formations. We conclude that the recurrence of a resected pituitary tumor may also represent a metachronous development of two distinct pituitary adenomas.

Heterogenous in vivo and in vitro expression of basic fibroblast growth factor by human pituitary adenomas.

Basic fibroblast growth factor (bFGF) is a potent mitogenic and angiogenic factor that is known to regulate GH, PRL, and TSH secretion. Sequences within a bFGF gene family member have been detected in transforming DNA samples derived from human PRL-secreting tumors. Furthermore, elevated serum concentrations of bFGF have been noted in patients with multiple endocrine neoplasia-1. To further examine the significance of bFGF in sporadic human pituitary adenomas, we investigated the expression of bFGF by these tumors. Using an enzyme-linked immunoassay that recognizes all 16-24 kilodalton molecular mass forms of bFGF, we measured circulating serum concentrations in 21 patients with sporadic pituitary adenomas; they ranged from less than 0.5-84 pg/mL and declined following surgical adenomectomy. To confirm the pituitary source of this growth factor, we determined in vitro bFGF release from 43 adenomas (10 GH, 7 PRL, 10 ACTH, 14 gonadotrope adenomas/oncocytomas, and 2 silent subtype 3 adenomas). bFGF was present with wide variability (0.75-2100 pg/24 h.10(5) cells) in conditioned culture media of all adenomas examined. The adenohypophysial source of this growth factor was further demonstrated by the reverse hemolytic plaque assay. Variable bFGF messenger RNA expression was identified by the reverse-transcription polymerase chain reaction technique in 9 functional (2 PRL, 5 GH, 2 ACTH) and 7 nonfunctional (1 oncocytoma, 2 null cell, 2 gonadotrope, 2 Silent Subtype 3) adenomas examined. bFGF levels were unaltered in vitro following hypothalamic hormone stimulation/inhibition. The lack of a bFGF signal peptide sequence and hypothalamic hormone-independence suggest that secretion of this factor may be independent of pituitary hormone regulation. Immunocytochemistry failed to localize bFGF in tumors that released this factor in vitro, suggesting that storage of this peptide does not correlate with its synthesis and release. In conclusion, the heterogenous expression of bFGF suggests that it may play a specific and selective role in the tumorigenic process of some pituitary adenomas.

Membrane-anchored expression of transforming growth factor-alpha in human pituitary adenoma cells.

Growth factors induce cell proliferation and are implicated in the multistep process of tumorigenesis. Transforming growth factor-alpha (TGF alpha), a peptide that binds to the epidermal growth factor receptor, is expressed by carcinomas and normal tissues. To investigate the possible role of TGF alpha in adenohypophysial tumorigenesis, we studied its expression in nontumorous human pituitary and different clinically and morphologically characterized human pituitary adenomas. Ribonucleic acid was reverse transcribed and amplified by polymerase chain reaction; transcript signals were identified with marked variation in 14 of 15 adenomas, and a weak signal was detected in nontumorous pituitary. Immunohistochemical positivity was found with variable intensity in all adenoma types, but not all tumors. Ultrastructural immunogold localized TGF alpha in endoplasmic reticulum, in Golgi apparatus, and on cell membranes; surface localization was confirmed by immunofluorescence. To assess possible secretion, the reverse hemolytic plaque assay was performed; small plaques were identified using an antibody that recognizes the extracellular domain of pro-TGF alpha; however, the plaques did not increase in size with time, suggesting that they detected membrane-anchored TGF alpha. Moreover, TGF alpha was undetectable by enzyme-linked immunosorbent assay in pituitary tumor-conditioned culture media. The marked variable expression of TGF alpha, the absence of secretion in measurable quantities, and the preferential membrane localization suggest a specific juxtacrine mechanism for TGF alpha in pituitary tumorigenesis.

Pituitary adenoma with neuronal choristoma (PANCH): composite lesion or lineage infidelity?

Fifteen cases of the rare association of pituitary adenoma and neuronal choristoma (PANCH) were investigated by histology, immunohistochemistry, and electron microscopy. Acromegaly was apparent clinically in 11 patients and was equivocal in 1, and 3 lesions appeared to be nonfunctioning. Histology revealed various proportions of chromophobic PA and nervous tissue consisting of neuronlike cells and neuropil. Immunohistochemistry documented growth hormone (GH) in every PA, including those unassociated with clinical acromegaly. In contrast, the NCH component showed no consistent immunohistochemical profile. Most frequent reactivities were for the pituitary hormone alpha subunit, thyroid-stimulating hormone, and GH, whereas only a few cases displayed scattered positivity for GH-releasing hormone. Low-molecular weight keratin tested positive in PAs and in a few cells and processes of an NCH. A few fibrous bodies were immunoreactive for neurofilament protein. Electron microscopy revealed sparsely granulated GH cell adenoma, neurons, and neuropil. Cells intermediate between PA and neurons were numerous in 1 lesion. The present morphologic findings as well as lack of GH cell hyperplasia and the consistent association of NCH with but one type of PA do not support the causative role of NCH in the initiation of PA, as proposed previously. It appears that NCH is the result of neuronal differentiation within sparsely granulated GH cell adenomas.

Prolactin-producing pituitary adenoma in a male-to-female transsexual patient with protracted estrogen administration. A morphologic study.

Pituitary adenoma developed in a 33-year-old male-to-female transsexual patient who was given estrogen, starting at 16 years of age; the pituitary adenoma was surgically removed and studied by light microscopy, immunocytochemistry, and in situ hybridization. The adenoma cells were immunoreactive for prolactin, and exhibited a strong signal for prolactin and estrogen receptor messenger RNAs and a weak signal for dopamine receptor messenger RNA. The question of whether the development of an adenoma was incidental or was the direct effect of estrogen or whether it was mediated via other mechanisms, such as activation of growth factors or oncogenes or inhibition of tumor-suppressing genes or other genetic abnormalities, remained unresolved. The present case, which, to our knowledge, is the first to describe structural findings of a pituitary adenoma in a transsexual patient who was given estrogen, reinforces the view that protracted stimulation may play a role in the genesis of endocrine tumors.

Somatotroph hyperplasia without pituitary adenoma associated with a long standing growth hormone-releasing hormone-producing bronchial carcinoid.

Acromegaly is most often associated with a pituitary somatotroph adenoma. While multiple lines of evidence suggest an intrinsic somatic cell defect in adenoma formation, the role of hypothalamic hormones in pituitary tumorigenesis remains unclear. We describe the functional and morphological features of the pituitary of a patient with a long-standing ectopic GH-releasing hormone (GHRH)-producing tumor and acromegaly. This 28-yr-old woman with a documented 10-yr history of a disseminated bronchial carcinoid was evaluated for clinical features of acromegaly. Elevated serum GH (88 micrograms/L) was not suppressed after glucose ingestion and was paradoxically stimulated by TRH, but did not respond to GHRH or GnRH administration. Serum insulin-like growth factor-1 (730 micrograms/L; normal, < 333 micrograms/L), insulin-like growth factor-binding protein-3 (9.5 mg/L; normal, 2-4.2 mg/L), and GHRH (26.1 micrograms/L; normal, < 20 ng/L) were elevated. Magnetic resonance imaging revealed a diffusely enlarged pituitary gland. Octreotide treatment for 4 months resulted in suboptimal clinical and biochemical responses. Examination of the transsphenoidally resected pituitary by light microscopy revealed diffuse somatotroph hyperplasia, with intact reticulin network and preservation of the acinar architecture. Electron microscopy showed active somatotrophs interspersed with other cell types. In situ hybridization revealed very strong positivity for GH mRNA, whereas fewer cells contained GHRH and somatostatin mRNA signals. Dispersed pituitary cells secreted GH into culture medium. GH release was stimulated by GHRH and GHRH plus TRH, but not by TRH alone; GH was suppressed by octreotide in vitro. We conclude that sustained exposure to ectopic GHRH leads to somatotroph hyperplasia, but, at least in this case, was not sufficient for adenomatous transformation.