垂体生长激素细胞腺瘤的电镜及免疫电镜观察

24 cases of growth hormone(GH)-producing pituitary adenomas were studied with electron microscopy and immunoelectron microscopy by protein A-gold complex, 6 cases were identified as densely granulated GH adenoma and 15 cases as sparsely granulated GH adenoma, among which 4 cases were proved by immunoelectron microscopy to be containing granules with prolactin(PRL) activity simultaneously. Intracytoplasmic fibrous bodies were often seen in the sparsely granulated cells anyhow, not all those cells with fibrous bodies possess the secretory granules with GH activity, and fibrous bodies were also detected in some PRL cells of certain mixed type adenoma. This suggests that fibrous bodies might not be the specific morphological feature of pituitary growth hormone cell adenomas.     

Growth hormone (GH) and prolactin (PRL) gene expression and immunoreactivity in GH- and PRL-producing human pituitary adenomas

Summary Growth hormone(GH)-producing pituitary adenomas are morphologically heterogeneous and frequently contain not only GH immunoreactivity but also variable numbers of prolactin (PRL) immunopositive cells. Paraffin sections of 59 surgically removed GH- and/or PRL-producing adenomas classified by histology, immunocytochemistry (ICC) and electron microscopy were studied using in situ hybridization (ISH) for GH and PRL mRNA and combined with ICC for the coded hormones. Somatotroph adenomas (10 densely and 10 sparsely granulated tumours) and mammosomatotroph adenomas (10 cases) contained both GH mRNA and GH immunoreactivity. In 4 densely and 4 sparsely granulated somatotroph adenomas and 4 mammosomatotroph adenomas, only GH mRNA and its product were found. In 28 cases (6 densely and 6 sparsely granulated somatotroph adenomas, 10 mixed somatotrophlactotroph adenomas and 6 mammosomatotroph adenomas) both GH and PRL mRNA were present, although no PRL immunoreactivity was not in 2 densely granulated somatotroph adenomas. In these cases, ISH for PRL mRNA combined with GH immunostaining revealed the presence of variable numbers of mammosomatotrophs. In 9 acidophil stem cell adenomas only PRL mRNA and its product were found; one tumour expressed both GH and PRL mRNA and their products. Nine lactotroph adenomas contained only PRL mRNA and PRL immunoreactivity. The results show that GH and/or PRL mRNA content could not be correlated with ICC for coded proteins and ultrastructural features. The mammosomatotrophs were more numerous using ISH when compared with ICC. Somatotroph, mammosomatotroph and mixed adenomas are closely related and they can be considered to represent one basic tumour type originating in a cell committed to GH production. This may undergo clonal differentiation towards a mammosomatotroph and further to the lactotroph line. The results also indicate that lactotroph adenomas arise in a cell committed to PRL production. Acidophil stem cell adenomas seem to be more closely related to lactotroph cells than somatotroph.     

Pituitary adenomas in acromegaly: Comparison of different adenoma types with clinical data

Adenoma tissues from 309 patients with active acromegaly was examined by routine light microscopy and immunohistochemistry, and selectively by electron microscopy. All adenomas were immunoreactive for growth hormone. Eighty-seven adenomas were monohormonal (28%), 58 were bihormonal (immunoreactive for growth hormone and prolactin) (19%), and 157 adenomas were plurihormonal (51%), with positivity for glyco-proteins and/or their α-subunit as well. The mean tumor size was significantly greater in monohormonal adenomas than in other adenoma types. There was no difference in invasiveness among the various adenoma types. Younger patients showed invasive tumor growth more often. Patients with densely granulated GH cell adenomas had a significantly longer duration of symptoms compared to patients with other adenoma types. More than half of the patients with sparsely granulated GH cell adenomas had a duration of less than 5 yr. There was no correlation between duration of symptoms and tumor size. The preoperative mean GH level was significantly higher in patients with sparsely granulated GH cell adenomas than in those with mixed GH/PRL cell adenomas. The preoperative mean PRL level was significantly higher in patients with bihormonal adenomas than in those with plurihormonal adenomas. There was an inverse correlation between age and preoperative GH and PRL levels. No linear correlation was found between preoperative basal GH and PRL levels. Monohormonal adenomas presented more often with suprasellar and/or parasellar extension than other adenoma types. Our data suggest a positive correlation between tumor extension and preoperative GH and PRL levels. Patients with plurihormonal adenomas were significantly older than patients with sparsely granulated GH cell adenomas and mixed GH/PRL cell adenomas. No significant difference was found between the various adenoma types and the extent of surgical removal, which depends on the degree of invasiveness, tumor size, and extrasellar tumor extension.     

An Atypical Acidophil Cell Line Tumor Showing Focal Differentiation Toward Both Growth Hormone and Prolactin Cells

We report a case of giant pituitary adenoma in a child. Computerized tomography (CT) scan revealed a suprasellar extension tumor mass with hydrocephalus. There was no clinical evidence of acromegaly, gigantism, and other hormonal symptoms. Endocrinologic studies showed within normal value of serum growth hormone (GH: 4.2 ng/mL) and slightly increased levels of prolactin (PRL: 78 ng/mL) and other pituitary hormone values were within normal range. On suppression test by bromocryptin, both GH and PRL levels were reduced. Histopathological findings revealed that the tumor consisted of predominantly chromophobic and partly eosinophilic adenoma cells. Immunohistochemical staining detected GH and PRL in a small number of distinctly different adenoma cells, respectively. Nonradioactivein situ hybridization (ISH) also showed GH and PRL mRNA expression in identical immunopositive cells. Electron microscopy (EM) demonstrated adenoma cells with moderate or small numbers of two types of dense granules and without fibrous body which are characteristic of sparsely granulated GH-cell adenomas. The adenoma does not fit into any classification but may be an atypical acidophil cell line tumor showing focal differentiation toward both GH and PRL cells.     

Pituitary adenoma in Carney complex: an immunohistochemical,ultrastructural, and immunoelectron microscopic study

First described in 1985, Carney complex is a rare, heritable disorder featuring abnormal skin pigmentation, cardiac and cutaneous myxoma, melanotic schwannoma of psammomatous type, and endocrine abnormalities, including pituitary adenomas. Patients with the latter present with elevated growth hormone (GH) levels and acromegaly or gigantism. Prolactin (PRL) elevation may also be seen. The authors have investigated 2 resected pituitary adenomas from patients with Carney complex. One, a 19-year-old female acromegalic with elevated GH, IgF-1, and PRL levels, had a mammosomatotroph adenoma immunoreactive for GH and PRL. Ultrastructurally, GH and PRL were present in the same secretory granules. The second patient, a 27-year-old acromegalic, had a sparsely granulated GH cell adenoma that by immuno-electron microscopy revealed GH immunoreactivity only. The lack of morphologic similarity between the 2 adenomas indicates that pituitary tumors in patients with Carney complex may not exhibit the same phenotype.     

Pituitary Adenoma in Carney Complex: An Immunohistochemical,Ultrastructural, and Immunoelectron Microscopic Study

First described in 1985, Carney complex is a rare, heritable disorder featuring abnormal skin pigmentation, cardiac and cutaneous myxoma, melanotic schwannoma of psammomatous type, and endocrine abnormalities, including pituitary adenomas. Patients with the latter present with elevated growth hormone (GH) levels and acromegaly or gigantism. Prolactin (PRL) elevation may also be seen. The authors have investigated 2 resected pituitary adenomas from patients with Carney complex. One, a 19-year-old female acromegalic with elevated GH, IgF-1, and PRL levels, had a mammosomatotroph adenoma immunoreactive for GH and PRL. Ultrastructurally, GH and PRL were present in the same secretory granules. The second patient, a 27-year-old acromegalic, had a sparsely granulated GH cell adenoma that by immuno-electron microscopy revealed GH immunoreactivity only. The lack of morphologic similarity between the 2 adenomas indicates that pituitary tumors in patients with Carney complex may not exhibit the same phenotype.     

Histopathological analyses of silent pituitary somatotroph adenomas using immunohistochemistry, in situ hybridization and confocal laser scanning microscopic observation

To characterize the morphological and functional aspects of silent somatotroph adenomas with paradoxical responses of GH in TRH or GnRH provocation tests, which are considered to be a useful strategy for endocrinological identification of silent somatotroph adenomas, we examined three silent somatotroph adenomas histopathologically. The adenomas were investigated by immunohistochemistry, including the highly sensitive catalyzed signal amplification system, the non-radioisotopic in situ hybridization method, and confocal laser scanning microscopy. GH production and GH-immunopositive secretory granules in the adenoma cells were demonstrated histopathologically, and the adenomas were interpreted as being densely granulated somatotroph adenomas. Endocrinological identification of silent somatotroph adenomas in combination with paradoxical responses of GH in TRH or GnRH provocation tests may elucidate the increasing number of silent somatotroph adenomas that have been regarded as mammotroph or clinically inactive adenomas. One should be aware of the differences between the previously reported silent somatotroph adenomas, most of which are sparsely granulated somatotroph adenomas, a somatotroph adenomas with paradoxical and the silent somatotroph adenomas, most of which are sparsely granulated somatotroph adenomas, and the silent somatotroph adenomas with paradoxical responses of GH in TRH or GnRH provocation tests, which are densely granulated somatotroph adenomas.     

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.     

Human growth hormone and prolactin secreting pituitary adenomas analyzed by in situ hybridization

Acidophilic pituitary adenomas commonly produce growth hormone (GH) or prolactin (PRL), according to studies employing immunohistochemical and ultrastructural methods. To examine this question, in situ hybridization with oligonucleotide probes was done on routinely processed tissues received in the pathology laboratory to analyze for the presence of GH and PRL messenger RNA (mRNA) in 4 normal pituitaries, 10 prolactinomas, and 16 GH-secreting adenomas. Most acidophilic cells in normal pituitaries expressed either GH or PRL hormone and the respective mRNAs, but GH mRNA and PRL hormone were also detected in some of the same cells. Patients with a clinical diagnosis of prolactinoma had cells with only PRL mRNA in their tumors, while most (14 of 16) patients with a clinical diagnosis of acromegaly or gigantism had both GH and PRL mRNAs in their tumors. The GH adenomas varied in these studies. In situ hybridization was helpful in characterizing the adenoma from a patient with acromegaly who had immunoreactive PRL, but no immunoreactive GH in the resected tumor; in situ hybridization analysis revealed mRNAs for both GH and PRL in the same tumor cells. Our findings indicate that pituitary adenomas from patients with acromegaly commonly express PRL mRNA. It is concluded that in situ hybridization provides new information about the clinical biology and the histopathologic classification of pituitary adenomas.     

Octreotide Effect on Growth Hormone and Somatostatin Subtype 2 Receptor mRNAs of the Human Pituitary Somatotroph Adenomas

Octreotide, a somatostatin analog used to treat acromegalic patients harboring a pituitary tumor, acts via somatostatin subtype 2 receptor (SSTR2) and causes significant decrease of circulating GH levels and sometimes mild to moderate tumor shrinkage. To further elucidate the mechanism of octreotide action, we studied GH and SSTR2 mRNAs by in situ hybridization in densely and sparsely granulated somatotroph adenomas removed by surgery from 14 treated and 14 untreated patients. Only in densely granulated adenomas were the GH and SSTR2 mRNA signals mildly decreased relative to untreated matched adenomas. The decrease of GH mRNA in densely granulated somatotroph adenomas suggests that they may have a more favorable response to octreotide therapy than sparsely granulated tumors.     

Ultrastructural Morphology of Folliculo-Stellate Cells in Human Pituitary Adenomas

Fifty-six pituitary adenomas were studied by electron microscopy in a search for the presence of folliculo-stellate cells (FSCs) with the aim of evaluating their prevalence and ultrastructural morphology. FSCs were scattered in two adenomas (one oncocytoma and one densely granulated GH cell adenoma) and were numerous in a sparsely granulated GH cell adenoma; their overall prevalence was 5.4%. Ultrastructural examination of the three neoplasms revealed that FSCs were hypertrophic element with abundant cytoplasm and organelles (in contrast to FSCs of the normal pituitary) and no obvious signs of neoplastic transformation. Junctional complexes between FSCs were similar to those described in the normal gland. Numerous follicular structures were lined by FSCs. FSCs in pituitary adenomas are probably nonneoplastic, reactive cells showing signs of hyperactivity, similar to FSCs found during pituitary hypersecretion and in estrogen-induced tumor.     

Protein kinase C (PKC) activity and PKC messenger RNAs in human pituitary adenomas.

Protein kinase C (PKC) is involved in the differentiation and growth regulation of a variety of tissues including anterior pituitary gland cells. To determine the distribution of PKC in different types of adenomas, PKC activity was analyzed in human pituitary tumors and the effects of hypothalamic hormone stimulation on PKC activity were examined in cultured adenoma cells. Gonadotroph (LH/FSH) and null cell adenomas had significantly higher levels of particulate, soluble, and total PKC activity compared with growth hormone (GH) adenomas (P < 0.05). Chronic stimulation of null cell adenomas with gonadotropin hormone-releasing hormone or of one GH adenoma with GH-releasing hormone for 7 days did not significantly alter total PKC activity in pituitary cells cultured in serum-free medium. Localization of the calcium-dependent PKC isozymes (alpha, beta and gamma) by immunohistochemistry and in situ hybridization revealed predominantly PKC alpha in all adenomas and variable expression of PKC beta and gamma in some tumors. When the calcium-independent PKC isozymes (delta, epsilon, and zeta) were localized by in situ hybridization, normal and neoplastic pituitaries expressed abundant mRNA for PKC epsilon, whereas some tumors and one normal pituitary had a few cells positive for PKC zeta mRNA as evaluated by grain density and the number of cells labeled. These results indicate that there is a variable distribution of PKC mRNA isozymes in human pituitary adenomas and that normal pituitaries and pituitary adenoma cells express the mRNA for both the calcium-dependent and some of the calcium-independent PKC isozymes. Chronic treatment with the hypothalamic gonadotropin hormone-releasing hormone and GH-releasing hormone, which increased LH/FSH and GH secretion, respectively, did not increase PKC activity in cultured adenoma cells. The presence of calcium-dependent and calcium-independent PKC isozymes in normal and neoplastic pituitary cells indicates that PKC probably plays a major role in signal transduction in the human pituitary adenomas examined in this study.     

Prolactin-producing pituitary adenoma associated with prolactin cell hyperplasia

A 24-yr-old woman with amenorrhea, galactorrhea, hyperprolactinemia, and sellar mass underwent transsphenoidal surgery. Histologic, immunohistochemical, and electron microscopic investigation revealed a well-differentiated, sparsely granulated prolactin (PRL) cell adenoma of the pituitary showing conclusive PRL immunoreactivity. In the nontumorous adenohypophysis PRL cell hyperplasia was noted. Marked differences were evident between the neoplastic and hyperplastic areas. The tumor consisted of sparsely granulated PRL cells immunoreactive only for PRL. As demonstrated by immunoelectron microscopy, the hyperplastic are a comprised monohormonal sparsely granulated PRL cells as well as bihormonal mammosomatotrophs immunoreactive for both PRL and growth hormone. The MIB-1 index was higher whereas microvessel density was lower in the adenoma as compared with the hyperplastic area. In addition, the nontumorous area showed lymphocytic infiltration whereas inflammatory reaction was not seen in the adenoma. This case represents a rare association of a PRL cell adenoma and PRL cell hyperplasia. The fact that these two lesions were contiguous in the surgically removed material raises the possibility that hyperplasia can precede and transform into adenoma.     

Heterogeneity of secretory granules of silent pituitary adenomas

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

Pituitary adenomas producing growth hormone in acromegalic patients.

Growth hormone was shown in histological sections of 25 pituitary adenomas from acromegalic patients by means of the unlabelled peroxidase-antiperoxidase (PAP) technique. On the basis of the numbers of cytoplasmic granules, the cells of the adenomas were of two types: densely granulated and sparsely granulated. The densely granulated cells had abundant cytoplasm containing numerous granules, whereas the sparsely granulated cells had little cytoplasm with scanty granules. Depending on the predominant cell type the adenomas were also classified as densely granulated or sparsely granulated: 21 of the 25 adenomas (84%) were densely granulated and four (16%) sparsely granulated. There was some variation, however, in the relative numbers of the two types of cell from one part of an adenoma to another, a feature consistent with one type of cell in different phases of activity. There was no significant difference in mean serum growth hormone concentrations between the two groups, and granularity of the adenomas in histological sections did not therefore correlate with secretory activity. Nine adenomas showed extrasellar extension. The mean serum growth hormone concentration in these cases was lower than the mean of the adenomas confined to the sella turcica. Thus the size of the tumour did not correlate with the serum growth hormone concentration. Three of the four adenomas in the sparsely granulated group showed extrasellar extension, compared with 6 of 21 classified as densely granulated. This suggests that sparsely granulated adenomas have a more aggressive pattern of behaviour, but histological evidence for this was lacking.     

Hybridization studies of cultured human pituitary prl and gh producing adenoma cells: Effects of thyrotropin-releasing hormone,somatostatin, and phorbol ester

The effects of the hypothalamic hormones, thyrotropin-releasing hormone (TRH), and somatostatin (SRIH), and of phorbol 12-myristate 13-acetate (PMA) on PRL and GH secretion and messenger RNA (mRNA) levels were analyzed in 10 GH and/or PRL producing adenomas after culturing the tumor cells in the presence of these secretagogues for 7 days. The expression of chromogranin A and B mRNAs was also examined. All four of the clinically diagnosed GH adenomas expressed or secreted both GH and PRL while four of six clinically diagnosed prolactinomas produced or secreted both PRL and GH. Prolactinomas had less than 10% of tumor cells expressing chromogranin A mRNA while more than 40% of the adenoma cells expressed chromogranin B mRNA. TRH stimulated PRL secretion and increased PRL mRNA levels while SRIH decreased GH secretion and mRNA expression in some cases. Unexpectedly, PMA stimulated PRL mRNA levels four- to sevenfold above control levels in two adenomas and generally stimulated chromogranin A and B mRNA expression but not GH mRNA, as determined by Northern hybridization and in situ hybridization analyses. These results indicate that cultured prolactinoma cells express significantly more chromogranin B mRNA than chromogranin A mRNA, and that PMA increases PRL mRNA expression in some prolactinomas, although the effect of PMA on various adenomas reflects the heterogeneity of these tumors with respect to protein kinase C stimulation.     

The effects of estrogens on tumor growth and on prolactin and growth hormone mRNA expression in rat pituitary tissues.

Estrogens inhibit tumor growth and modify PRL and GH expression in the MtT/W15 transplantable rat pituitary tumor. The effects of estradiol (E2) and diethylstilbestrol (DES) on PRL and GH mRNA levels were investigated. Estrogens increased GH mRNA levels and decreased PRL mRNA levels as detected by in situ hybridization and Northern blot hybridization with oligonucleotide probes, while inhibiting tumor growth. Similar changes in immunoreactive GH and PRL were seen in the tumor cells. The pituitary glands of tumor-bearing rats treated with estrogen for 3 weeks were increased in weight with a concurrent increase in pituitary PRL mRNA when analyzed by dot blot hybridization. These results indicate that estrogens have an inhibitory effect on the growth of the MtT/W15 tumor and increase GH protein and mRNA levels, while causing PRL protein and mRNA levels to decrease. The pituitaries of tumor-bearing rats concomitantly undergo PRL cell hyperplasia with an increase in PRL mRNA. These results also demonstrate a paradoxical effect of estrogens on different pituitary tissues.