Vascularization of rat pituitary autografts

Pituitary autotransplantation eliminates direct vascular contact between the hypothalamus and the adenohypophysis, and enables us to study the role of the hypothalamus in regulating adenohypophysial endocrine activity. The aim of this study was to investigate vascularization of the pituitary autografts. Three-month-old male Wistar rats were hypophysectomized, and their adenohypophyses were autotransplanted under the renal capsule. The animals were killed 3 weeks after autotransplantation. The grafts were removed and studied by using histology, immunohistochemistry and transmission electron microscopy. In the central portion of the grafts, organizing necrosis was apparent. The peripheral portion of the graft contained all adenohypophysial cell types, with a predominance of lactotrophs. Vascular endothelial growth factor and hypoxia-inducible factor were expressed in the graft mainly in the perinecrotic areas. Several capillaries inside the grafts were lined by continuous unfenestrated epithelium, while others were lined by fenestrated endothelium, suggesting that neovascularization is the result of two processes: ingrowths of capillaries from the renal capsule to the graft, and neoformation of capillaries from pre-existing adenohypophysial vessels. In conclusion, hypoxia seems to be an important factor in the vascularization of pituitary autografts. Mediated via hypoxia-inducible factor, hypoxia stimulates vascular endothelial growth factor secretion, which plays a crucial role in angiogenesis.

Pathobiology of Pituitary Adenomas and Carcinomas

OBJECTIVE

To examine relationships between pituitary tumors and lesion size, invasiveness, resectability, deoxyribonucleic acid ploidy, cell cycle profile, mitotic activity, and immunoreactivity for MIB-1, proliferating cell nuclear antigen (PCNA), p27Kip1, and p53.

PATIENTS AND METHODS

One hundred fifty-three adenomas of most pathological subtypes, including 20 medically treated and prolactin and growth hormone-containing tumors, as well as 10 premetastatic tumors and 13 pituitary carcinomas, were studied.

RESULTS

Significant (P < 0.05) differences were noted between functional versus nonfunctional adenomas (percent aneuploidy, percent S phase, p27Kip1 labeling indices [LI], male sex, tumor size, and frequency of visual disturbance); Cushing's versus silent adrenocorticotropin adenomas (percent hypertetraploidy, p53 LI, tumor size, visual disturbance, and resectability); untreated versus medically treated prolactin cell adenomas (MIB-1 LI, p53 LI, and resectability); untreated versus medically treated growth hormone-containing adenomas (percent diploidy, percent S phase, MIB-1 LI, p53 LI, and p27 LI); untreated prolactin cell adenomas versus premetastatic tumors (percent hypertetraploidy, PCNA LI, p53 LI, invasiveness, and resectability); untreated growth hormone-containing adenomas versus premetastatic tumors (percent diploidy, percent S phase, PCNA LI, p53 LI, invasiveness, and resectability); Cushing's adenomas versus premetastatic tumors (percent diploidy, percent hypertetraploidy, percent S phase, MIB-1 LI, p53 LI, tumor size, invasiveness, visual disturbance, and resectability); Nelson's adenomas versus premetastatic tumors (p53 LI, tumor size, invasiveness, and resectability); silent adenomas as a whole versus nonfunctional adenomas (percent nondiploid, percent S phase, invasiveness, and respectability); silent adrenocorticotropin adenomas I and II versus silent adenoma Subtype III (invasiveness); silent adrenocorticotropin adenoma Subtypes I and II versus premetastatic tumors (MIB-1 LI and invasiveness); silent adenoma Subtype III versus premetastatic tumors (PCNA and p53 LI); and premetastatic tumors versus metastatic pituitary carcinomas (MIB-1 LI).

CONCLUSION

Only trends toward differences were noted between Cushing's versus Nelson's adenomas and between prolactinomas of reproductive female patients versus those of menopausal female patients and male patients. Too few "atypical adenomas" were encountered to permit their comparison with premetastatic tumors, but our results suggest that most pituitary carcinomas arise by malignant transformation from adenomas.

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.

Immunohistochemical expression of nestin in the non-tumorous hypophysis and in pituitary neoplasms

The aim of the present work was to investigate whether nestin, a member of the intermediate filament family, is immunohistochemically expressed in the non-tumoral human hypophysis and pituitary neoplasms. Twenty-three normal pituitaries and 125 pituitary neoplasms were included. The tissues were formalin-fixed and paraffin embedded. The neoplasms were identified on hematoxylin-eosin stained sections and were classified by immunohistochemistry as well as electron microscopy. For immunohistochemistry, the streptavidin-biotin-peroxidase complex method was applied using appropriate controls. Several corticotrophs in the autopsy obtained pituitaries showed cytoplasmic nestin immunopositivity. No nestin immunoreactivity was found in other cell types in non-tumorous adenohypophyses and in the cells of various pituitary adenomas. Nestin was, however, expressed in a small proportion of endothelial cells in both anterior and posterior lobes. Staining was also noted in several pituicytes, neurohypophysial nerve fibers, and Herring bodies. In contrast to CD-34 and Factor-8 immunostaining which demonstrated immunopositivity in practically all endothelial cells of every capillary, nestin expression was only focally seen suggesting that the functional status of the immunoreactive and non-staining endothelial cells was not the same. No statistically significant correlation was apparent between nestin immunoreactivity and patient age, gender, tumor size, mitotic index, Ki-67, labeling nuclear index, hormonal immunoprofile, and tumor type. In conclusion, nestin expression in adenomas cannot be viewed as a biologically relevant marker of cell proliferation and as a prognostic indicator. The patchy expression of nestin in endothelial cells remains unexplained and its significance requires further studies.

Pituitary corticotroph hyperplasia preceding adenoma in a patient with Nelson's syndrome

We report the case of a 42-year-old woman with Cushing's disease and Nelson's syndrome. When she was 17 years old, transsphenoidal surgery was performed. A detailed morphologic study demonstrated nodular hyperplasia of corticotroph cells but no adenoma. Following a long-lasting remission (14 years), Cushing's disease recurred. After an unsuccessful second transsphenoidal surgery, Cushing's disease persisted and both adrenals were removed (at the age of 34). Subsequently the patient developed Nelson's syndrome. The pituitary tumor proved to be a corticotroph adenoma; it was removed by the transsphenoidal approach (at the age of 42). Although in most patients Cushing's disease is due to an ACTH-secreting pituitary corticotroph adenoma which precedes the manifestation of Nelson's syndrome, our case indicates not only that corticotroph hyperplasia may cause Cushing's disease but that it may exist before the development of Nelson's syndrome after the removal of both adrenals. Our study supports the view that protracted stimulation of corticotrophs resulting from the elimination of the negative inhibitory feedback effect by corticosteroids plays a role in adenoma initiation.

Prognostic indicators in an aggressive pituitary Crooke's cell adenoma

OBJECTIVE

To investigate prognostic indicators in an aggressive Crooke's cell adenoma of the pituitary.

METHODS

The surgically removed tumor was studied by histology, immunohistochemistry and transmission electron microscopy.

RESULTS

An aggressive invasive sellar tumor removed by repeated surgeries from a 43-year-old woman with pituitary related Cushing's disease was classified as a Crooke's cell adenoma of the pituitary. The application of several cell proliferation markers confirmed the aggressive nature of the tumor.

CONCLUSIONS

The investigation of the present case provides additional evidence that pituitary Crooke's cell adenomas may possess aggressive behavior.

Plurihormonality in pituitary adenomas associated with acromegaly

Bihormonal or plurihormonal pituitary tumors produce two or more hormones different in chemical composition, immunoreactivity, and clinical significance. Immunohistochemical and electron microscopic investigations and more recently molecular-genetic studies have provided conclusive evidence of the production of multiple hormones by pituitary adenomas. Most frequently, they produce GH, PRL, TSH, and/or alpha-subunit of the glycoprotein hormones. Other uncommon combinations may also be apparent. We report the case of a 40-yr-old acromegalic man with a pituitary macroadenoma. The pituitary tumor was removed by transsphenoidal surgery. Histological, immunohistochemical, electron microscopic, and immunoelectron microscopic examinations revealed that the tumor contains multiple hormones (GH, LH, and alpha subunit) and transcription factors. The application of different reagents yielded different patterns of positivity indicating that the validity of some common immunohistochemical reagents must be re-evaluated.

Morphologic changes of prolactin-producing pituitary adenomas after short treatment with dopamine agonists

Treatment of patients with prolactin (PRL)-producing pituitary adenomas with dopamine agonists has proved successful for most cases. Dopamine agonists inhibit PRL secretion, suppress cell proliferation, and may induce apoptosis to adenoma cells. Dopamine agonists induce striking morphologic changes in the majority of treated PRL-producing adenomas. To date, these morphologic effects have been primarily described only after long-term treatment. To the best of our knowledge, no similar studies have investigated apoptotic alterations induced after short-term therapy. The purpose of this report is to describe the morphologic changes seen in PRL-producing adenomas after short-term dopamine agonist treatment. We present two cases of PRL-producing macroadenomas, both from male patients who received treatment with dopamine agonists, the first for 5 and the second for 8 days. In contrast to long-term treatment, no striking reduction of PRL immunoreactivity was noted. Slight stromal fibrosis was noted in case 1, which contained several cells all in late phase of apoptosis. In addition to typical apoptotic cells, numerous "dark" cells representing another common form of cell death were also noted. These novel findings represent characteristic features of short-term dopamine agonist treatment, which are not seen in long-term treatment.

Pathology of acromegaly

This review summarizes current knowledge on pituitary changes in patients with acromegaly. The histologic, immunohistochemical and electron microscopic study provided conclusive evidence that a marked diversity exists between the tumors which secrete growth hormone (GH) in excess, such as densely and sparsely granulated GH cell adenoma, the mixed GH prolactin cell adenoma and the mammosomatotrope adenoma. The latter two tumors produce GH and prolactin simultaneously. Densely granulated GH cell tumors may produce thyrotropin and alpha subunit as well. Somatotrope carcinomas are extremely rare. GH cell hyperplasia can also be associated with acromegaly in patients with extrapituitary GH-releasing hormone secreting tumors. The medical therapy of acromegaly is reviewed briefly, including long-acting somatostatin analogs and pegvisomant, a GH receptor blocker.

Diversity of ACTH-immunoreactive cells in the human adenohypophysis: an immunohistochemical study with special reference to cluster formation and follicular cell association

Horvath et al. called relatively small ACTH-immunoreactive (ACTH-IR) cells observed in basophil invasion "proopiomelanocortin (POMC) cells," and these cells were supposed to be different from larger ACTH-IR cells in human adenohypophysis. To clarify the existence of "anterior POMC cells," we examined 21 autopsy cases taking note of follicular cells (FCs). We found that smaller ACTH-IR cells were clustered forming small areas without FC association, clustered small cell island (CSCI). CSCI was found in all the specimens we examined using immunohistochemical staining for ACTH and cytokeratin (AE1/AE3) in serial sections. ACTH-IR cells outside CSCI were of various sizes, mainly consisting of larger ACTH-IR cells that were diffusely scattered among other hormone-secreting cells and closely associated with FCs. By immunohistochemistry, ACTH-IR cells within CSCI and basophil invasion showed uniformly weak reactivity and common patterns for cytokeratins (CAM5.2 and 35 beta H11), carboxypeptidase D, and LeuM1, whereas those outside CSCI showed a great variety of immunoreactivity. The similarity in the immunoreactivity of ACTH-IR cells between CSCI and basophil invasion suggests that ACTH-IR cells in these two areas have common characteristics and ACTH-IR cells in CSCI are most likely "POMC cells." The clustered "anterior POMC cells" may be distinguishable by light microscopic immunohistochemistry.

Immunohistochemical study on so-called follicular cells and folliculostellate cells in the human adenohypophysis

Non-hormone-secreting cells in human adenohypophysis have been designated as either follicular cells (FC) or folliculostellate cells (FSC). They have similarly long cytoplasmic processes, and the difference between FC and FSC remains unclear. An immunohistochemical study for S-100 protein, cytokeratin (CK, detected by AE1/AE3) and glial fibrillary acidic protein (GFAP) was performed in autopsy pituitaries. Double immunohistochemistry for S-100 protein and CK revealed that there were numerous coexpressed cells. The most frequent type ('CK-type cell') was cells weakly positive for S-100 protein in the nucleus and for CK-immunoreactivity in the cytoplasm. The next numerous type ('S-100 protein cell') was cells strongly positive for S-100 protein and weakly positive or negative for CK. The CK-type cells were frequently observed in the vicinity of follicular structures and in neighborhood of adrenocorticotropic hormone -immunoreactive cells, and were most likely the cells termed FC. They were often observed around necrotic areas. The S-100 protein cells were individually found in the circumference of endocrine cell nest, and seemed to be the so-called stellate cells. GFAP-positive cells were rare. It is implied that S-100 protein-positive FSC could be divided into at least two main subtypes: FC (CK-type cells) and stellate cells (S-100 protein cells).

Effects of medical therapy on pituitary tumors

Previously surgery and irradiation were the only available procedures to treat patients with pituitary tumors. During the last few decades, novel drugs such as dopamine agonists and long-acting somatostatin analogs were developed and, an alternative medical therapy emerged. This paper summarizes the effect of medical therapy on the morphologic features of pituitary tumors and illustrates the ultrastructural alterations on electron micrographs. Currently drugs can be used in the management of pituitary tumors secreting GH, PRL, and/or TSH in excess. No medical therapy is available so far for ACTH-, FSH-, LH-, or alpha-subunit-secreting tumors as well as non-hormone-secreting pituitary tumors. Dopamine agonists are effective in the management of PRL-secreting tumors; they cause marked reversible tumor shrinkage in the substantial majority of patients. Long-acting somatostatin analogs are useful in the management of GH- and TSH-secreting pituitary tumors; they lead to mild to moderate tumor shrinkage in approximately 50% of cases. In patients treated with these drugs reduction of elevated blood hormone levels and amelioration of clinical symptoms ensue. It should be emphasized that no permanent cure is obtained. Blood hormone levels increase and the clinical symptoms reappear after discontinuation of treatment. Recently GH receptor blockers (pegvisomant) were introduced in the treatment of GH-producing pituitary adenomas. To the authors' knowledge the effect of these drugs on the morphology of pituitary tumors has not been revealed so far.

Ectopic bioactive luteinizing hormone secretion by a pancreatic endocrine tumor, manifested as luteinized granulosa-thecal cell tumor of the ovaries

Endocrine pancreatic tumors are rare neoplasms consisting of multipotent cells capable of secreting various bioactive substances causing characteristic clinical syndromes. Ovarian stromal hyperthecosis is characterized by varying degrees of luteinized stromal cell proliferation after sustained LH and/or human chorionic gonadotropin stimulation, clinically manifested by symptoms/signs of virilization resembling the polycystic ovary syndrome (PCOS). We report a case of ectopic bioactive LH production from a pancreatic endocrine tumor in a 33-yr-old woman with rapidly developing symptoms/signs of hyperandrogenism and markedly elevated serum androgen and LH levels leading to hyperthecosis and bilateral luteinized granulosa-thecal cell tumors of the ovaries. Although the patient was initially thought to have either severe PCOS or an LH-secreting pituitary tumor, an LH-producing pancreatic endocrine tumor bearing somatostatin receptors was demonstrated on scintigraphy with [111In]octreotide and abdominal imaging. Symptoms and signs of hyperandrogenism resolved after the resection of the tumor. Immunohistochemistry, in situ hybridization, and electron microscopy studies confirmed LH synthesis by the tumor cell. Although extremely rare, ectopic LH production from nonpituitary endocrine tumors should be considered in the differential diagnosis of hyperandrogenism, particularly when associated with highly elevated serum LH levels.

Pituitary adenoma: a DNA flow cytometric study of 192 clinicopathologically characterized tumors

A clinically, immunohistochemically and ultrastructurally characterized series of 192 pituitary adenomas was analyzed for DNA content by flow cytometry. Results were assessed not only relative to tumor immunotype, size, and invasiveness, but also with frequency of recurrence. Case selection was non-random; males predominated (1.8:1) and the ratio of macro-to-microadenomas was 4.2:1. Female patients were slightly younger and, in all adenoma categories, less often had invasive tumors: PRL (15%/30%), ACTH (17%/44%), LH/FSH (8%/27%) and null cell adenomas (0%/27%). With the exception of prolactin cell adenomas, similar proportions of macroadenomas and invasive tumors in all tumor subtypes were diploid and non-diploid. Prolactin adenomas differed in that tumors of males showed a high rate of non-diploidy (65%); such tumors were predominantly macroadenomas, but only 28% were invasive. Among GH-containing tumors 78% were macroadenomas, 40% were nondiploid, and the frequency of invasive macroadenomas was higher (49%) than in PRL tumors (21%). ACTH adenomas were mainly microadenomas (81%), their rate invasion (29%) and of non-diploidy being low (14%). Among "non-functioning" (LH/FSH, null cell adenomas), LH/FSH-producing tumors were all macroadenomas, but with low rates of invasion (23%) and non-diploidy (9%). Null cell adenomas, nearly all macroadenomas, had similar low invasion rate (21%), but were more often non-diploid (39%). In all adenoma subgroups S-phase fractions were higher in non-diploid adenomas by an overall ratio of 2.1:1. Prolactin adenomas showed the highest (15.2%) and LH/FSH adenomas the lowest (5.6%) mean S-phase fraction. When compared to long-term follow-up, neither this parameter nor ploidy correlated with tumor size or invasiveness. Lastly, long-term follow-up showed ploidy to be an unreliable predictor of tumor persistence or recurrence.

Galectin-3 Expression in Functioning and Silent ACTH-Producing Adenomas

Galectin-3 (Gal-3), a beta galactoside-binding protein, has been implicated in a variety of biological functions including cell growth, differentiation, tumor cell adhesion, angiogenesis, tumor progression, and metastasis. We recently reported that Gal-3 was expressed in a subset of normal pituitary cells and tumors including PRL, ACTH, and in folliculo-stellate (FS) cells and tumors and that Gal-3 had an important regulatory role in pituitary cell proliferation. We further investigated the expression of Gal-3 protein in ACTH- and PRL-producing tumors and the expression of various galectin mRNAs by RT-PCR in pituitary adenomas and normal pituitary. Most silent ACTH subtypes 1 and 2 adenomas were negative or only focally positive for Gal-3 expression compared to functioning ACTH tumors from patients with Cushing's disease and Nelson's syndrome. In the normal pituitary, Gal-3 was expressed in less than 1% of the basophil-invading cells (ACTH cells present in the posterior pituitary) and in a subset of the anterior lobe ACTH-positive cells. RT-PCR analyses showed that many members of the galectin family including galectins 1, 2, 3, 4, 5, 6, 7, 8, and 9 were expressed in normal pituitary and in functioning ACTH- and PRL-producing tumors. These results indicate that Gal-3 is associated with functioning ACTH and PRL tumors and is expressed infrequently in silent ACTH adenomas, suggesting that Gal-3 protein and/or gene is altered in non-functioning ACTH tumors. The use of ACTH and Gal-3 immunostaining should help in the diagnosis of silent ACTH adenomas.

The pituitary in Turner syndrome

Although Turner syndrome is not uncommon, studies of the pituitary in this condition are few. We undertook a histochemical and immunohistochemical study of four cases. As expected, "gonadal failure cells" were seen, but without recognizable gonadotroph hyperplasia. No gonadotroph adenomas were encountered. Instead, three silent corticotroph microadenomas were seen; their etiology remains unexplained. The question of whether the simultaneous occurrence of Turner syndrome and silent corticotroph adenoma is causal or incidental cannot be answered on the basis of the study of our material. Because these two diseases are rare, an etiologic association has to be considered. For example, it is possible that (a) protracted stimulation of gonadotrophs leads to transdifferentiation to corticotrophs, a hypothesis supported by the fact that normal and neoplastic gonadotrophs can contain ACTH and that some corticotroph adenomas produce LH and/or alpha subunit, (b) corticotrophs develop gonadotropin-releasing hormone (GnRH) receptors and undergo neoplastic transformation when exposed to continuous elevation of GnRH, FSH, and/or LH levels, and (c) the genetic defect in Turner syndrome promotes the formation of corticotroph adenomas.

Increased zinc content in transplastomic tobacco plants expressing a polyhistidine-tagged Rubisco large subunit

Rubisco is a hexadecameric enzyme composed of two subunits: a small subunit (SSU) encoded by a nuclear gene (rbcS), and a large subunit (LSU) encoded by a plastid gene (rbcL). Due to its high abundance, Rubisco represents an interesting target to express peptides or small proteins as fusion products at high levels. In an attempt to modify the plant metal content, a polyhistidine sequence was fused to Rubisco, the most abundant protein of plants. Plastid transformation was used to express a polyhistidine (6x) fused to the C-terminal extremity of the tobacco LSU. Transplastomic tobacco plants were generated by cotransformation of polyethylene glycol-treated protoplasts using two vectors: one containing the 16SrDNA marker gene, conferring spectinomycin resistance, and the other the polyhistidine-tagged rbcL gene. Homoplasmic plants containing L8-(His)6S8 as a single enzyme species were obtained. These plants contained normal Rubisco amounts and activity and displayed normal photosynthetic properties and growth. Interestingly, transplastomic plants accumulated higher zinc amounts than the wild-type when grown on zinc-enriched media. The highest zinc increase observed exceeded the estimated chelating ability of the polyhistidine sequence, indicating a perturbation in intracellular zinc homeostasis. We discuss the possibility of using Rubisco to express foreign peptides as fusion products and to confer new properties to higher plants.

Prolactin-producing pituitary adenoma with incomplete neuronal transformation: an intermediate adenoma-neuronal tumor

We present a unique case of a prolactin (PRL)-producing pituitary adenoma showing incomplete neuronal differentiation without ganglion cells. A 27-year-old man presented with nausea, headaches, and instability over the last 2 months. Clinical examination revealed obesity with no other endocrinological signs. His serum PRL levels were slightly elevated (38 ng/ml), whereas concentrations of the other adenohypophysial hormones were within normal range. Histology revealed an unusual pituitary adenoma containing many hypocellular areas with fibrillar appearance. The sizable tumor cells were polyhedral or elongated harboring an ovoid, vesicular nucleus with prominent nucleolus, lacking, however, the typical features of ganglion cells. By immunohistochemistry, many adenoma cells were positive for PRL. Immunostain for neurofilament protein revealed variable amounts of fibrils dispersed throughout the stroma, mostly in the hypocellular areas. In addition, neurofilament protein and chromogranin were strongly reactive in approximately 15% of the tumor cell population, whereas reactivity for synaptophysin was uniform throughout the tumor. These findings led to the conclusion that part of the tumor-cell population expressed a hybrid immunoprofile of adenoma-neuronal cell. Our case is the first PRL-producing pituitary adenoma showing incomplete neuronal differentiation lacking mature ganglion cells.

Morphology, Molecular Regulation and Significance of Apoptosis in Pituitary Adenomas

Apoptosis represents energy-requiring spontaneous single cell death, with specific morphologic and biochemical features. It is a rapidly processed sequence of events resulting in elimination of damaged cells. Apoptosis occurs in physiological remodeling and proliferative conditions, and also in neoplastic lesions. Several molecules and molecular systems such as bcl-2/bax, Fas/FasL and caspases regulate the apoptotic process. Apoptosis is characterized by a stereotypic pattern of morphologic features, which can be illustrated mostly by electron microscopy. DNA and biochemical assays, based on the specific pattern of nucleosomal fragmentation can detect apoptosis. The in situ labeling techniques are currently used to demonstrate apoptosis in paraffin sections. Several studies of pituitary animal models, cell lines and human pituitaries have been performed during the last 6 years. By electron microscopy, pituitary adenoma cells undergoing apoptosis exhibit a common prototypical pathway of changes. Although the results by the situ labeling techniques are not uniform, apoptosis occurs with low frequency in a subset of pituitary adenomas, in carcinomas and in pituitary hyperplasia. Alternative techniques based on remodeling of cytoskeleton by caspase activity can identify early apoptotic stages. This review presents the principles of apoptosis and summarizes the morphologic and functional changes of apoptosis in pituitary.

Expression of caveolin-1 and caveolin-2 in the human pituitary: an immunohistochemical study

Caveolins are coat proteins of caveolae, the plasmalemmal transport vesicles. To our knowledge their presence in the human pituitary and various types of hypophysial adenomas has not been investigated. In the present work, expression of caveolin-1 and caveolin-2 was studied by immunohistochemistry using the streptavidin-biotin-peroxidase complex method. The material included 7 autopsy obtained, 5 surgically removed non-tumorous pituitaries, and 97 hypophysial adenomas classified on the basis of histologic immunohistochemical and ultrastructural features. No immunoreactivity was seen for caveolin-1 and caveolin-2 in non-tumorous adenohypophysial and neurohypophysial cells and in the tumor cells, indicating that caveolins are not involved in the initiation and progression of pituitary adenomas. The expression of caveolin-1 and caveolin-2 in the endothelial cells did not depend on age, gender, endocrine status of the patients, morphologic features, and type of pituitary tumors. Scattered endothelial cells were immunopositive for both caveolins showing similar cytoplasmic localization. Evidence that the two caveolins were indeed localized to the same endothelial cell was demonstrated on consecutive sections using Factor-8 and CD-34, two reliable endothelial cell markers. Not every endothelial cell was immunoreactive for the two caveolins, suggesting that the functional status of endothelial cells is not the same within the adenomas, not even in the same capillary.

Pituitary pathology in Erdheim-Chester disease

Pituitary morphologic changes in patients with Erdheim-Chester disease have not been described in detail. We report here the histologic and immunohistochemical findings in the autopsy obtained pituitary of a 35-yr-old woman with extensively disseminated Erdheim-Chester disease. The posterior lobe was completely replaced by xanthogranulomatous infiltrates, providing an explanation for the patient's diabetes insipidus. The anterior lobe was intact and immunohistochemistry demonstrated expression of GH, TSH, FSH, LH, and alpha subunit within the normal range. A clinically observed decrease of anterior pituitary function was interpreted as hypothalamic in origin due to massive destruction of the hypophysial stalk and compression of the hypothalamus. Prolactin immunoreactive cells were numerous, consistent with the view that prolactin cell hyperplasia resulted from the loss of hypothalamic dopaminergic inhibition. Massive Crooke's hyalinization in the ACTH-producing cells was considered unrelated to Erdheim-Chester disease and was the consequence of treatment with pharmacologic doses of glucocorticoid hormones. It can be concluded that prolactin cell hyperplasia may be the only finding in the adenohypophysis of patients with disseminated Erdheim-Chester disease. It appears that in our patient the clinically apparent anterior hypopituitarism was not due to the lack of storage but rather to insufficient release of adenohypophysial hormones caused by the defect in hypothalamic regulation.

Humoral hypercalcemia of malignancy due to bipartite squamous cell/small cell carcinoma of the esophagus immunoreactive for parathyroid hormone related protein

We report the case of a 63-year-old man who presented with weakness, fatigue, dehydration, confusion, abdominal pain, congestive heart failure and hypercalcemia. He expired and autopsy revealed an exulcerating carcinoma of the esophagus, invading the esophageal wall and metastasizing to the lungs, skin and lymph nodes. Histology demonstrated an epithelial tumor consisting of two components with transition between the two. One component was a keratinizing squamous cell carcinoma, whereas the other component consisted of pleomorphic small cells. The hypercalcemia was assumed to be due to parathyroid hormone related protein (PHRP), which was demonstrated by immunohistochemistry only in the pleomorphic small cells and not in the squamous cells. PHRP induced humoral hypercalcemia of malignancy is most often associated with squamous cell carcinomas. The finding that in our case, the pleomorphic small cell component was PHRP immunopositive and the squamous cell component showed no immunoreactivity, is intriguing and remains unexplained.

Crooke's cell adenoma of the pituitary: an aggressive variant of corticotroph adenoma

Cushing's disease is caused by functional corticotroph adenomas of the pituitary, mostly noninvasive microadenomas. Classic Crooke's cells are nonneoplastic corticotrophs with cytoplasmic accumulation of cytokeratin filaments in response to glucocorticoid excess. Corticotroph adenomas exhibiting Crooke's change are rare and incompletely understood. We intend to define more clearly the clinicopathological features of Crooke's cell adenomas (CCA). Thirty-six CCAs were retrieved from the files of Mayo Clinic and from our (B.W.S., K.K.) consultation files. The number of informative cases varied for different criteria. Clinical follow-up was obtained in 31 cases. The 27 females and 9 males were 18 to 81 years of age (mean 46 years). At presentation, Cushing's disease was evident in 22/34 (65%); 81% were macroadenomas and 72% were invasive. All were initially treated by transsphenoidal resection. Twenty-five patients were followed for more than 1 year (mean 6.7 years). Of these, 15 (60%) developed recurrent tumor, and 6 (24%) had multiple recurrences. Lastly, 3 of these 25 patients (12%) died of tumor: 1 after multiple local recurrences and 2 from pituitary carcinoma. Compared with typical corticotroph adenomas, CCAs are aggressive. Most are functional adenomas occurring in middle-aged women and are invasive macroadenomas prone to recurrence. Morbidity and mortality rates are substantial. CCAs represent a distinct entity that should be separated from corticotroph adenomas without Crooke's hyaline change.

Gonadotropic pituitary carcinoma: HER-2/neu expression and gene amplification. Report of two cases

The authors report on two gonadotropic carcinomas of the adenohypophysis that occurred in a55-year-old man (Case 1) and a 53-year-old woman (Case 2), with signs of mass effect and amenorrhea, respectively. Both lesions were macroadenomas. The tumor in Case 1 metastasized to dura mater, skull, nasal sinus, and larynx 2 years after patient presentation, whereas that in Case 2 spread to vertebral bodies and ribs after a 19-year latency. Histologically, the primary, recurrent, and metastatic lesions in Case 1 featured brisk mitotic activity and high MIB-1 levels as well as p53 labeling indices. Immunoreactivity for HER-2/neu was assessable only in rare neoplastic cells of the second recurrence and in 80% of cells of the dural metastasis. Low-level HER-2/neu gene amplification was evident in the recurrent tumors and metastasis. The sellar and metastatic tumors in Case 2 resembled benign gonadotropic adenoma with oncocytic change; p53 accumulation, HER-2/neu overexpression, and HER-2/neu gene amplification were not present. The results indicate that low-level amplification of the HER-2/neu gene might be associated with pituitary carcinomas in which more aggressive behavior is seen. Further studies are needed to determine whether HER-2/neu plays a role in the pathogenesis of pituitary carcinoma.