Horváth, Éva

Objective MGMT expression in brain and pituitary tumors has been correlated with temozolomide treatment. Few medical therapies are available in patients with Nelson Syndrome. The aim of the present study was to assess immunohistochemical expression of MGMT in ACTH‐secreting pituitary adenomas in patients with Nelson Syndrome. Methods Our material consisted of specimens from ACTH‐secreting pituitary adenomas from patients with Nelson Syndrome. Immunohistochemical staining for MGMT was performed using the streptavidin‐biotin‐peroxidase complex method. MGMT immunoreactivity was assessed microscopically and recorded as an estimated percentage of nuclear MGMT immunopositivity. (0=none, 1=<10%, 3=<50%, 4=>50%) Results Male:Female ratio was 3:5, with average patient age being 62 (range 57–66). Five of the eight specimens (65%) exhibited no MGMT immunoreactivity, with two out of eight cases (25%) showing slight MGMT immunopositivity and one out of eight cases (12%) demonstrating moderate MGMT immunopositivity (<25%). Conclusions Temozolomide therapy may be useful in patients with Nelson Syndrome. Absent or low MGMT staining in brain and other neoplasms has been shown to correlate with successful treatment with temozolomide, and recent reports assessing aggressive pituitary adenomas suggest similar outcome.

SNAP‐25, a synaptosome associated exocytosis protein of 25 kDa plays an important role in the secretory activity of several endocrine cells. In the present study, we investigated 15 PRL, 10 GH, 5 ACTH, 5 TSH, 15 FSH/LH/ alpha subunit producing, and 5 null cell adenomas. Surgically removed, formalin‐fixed and paraffin embedded human pituitary tumors were used. Sections were immunostained by the streptavidin‐biotin‐peroxidase complex method. The results showed that 10 PRL producing adenomas were strongly immunoreactive for SNAP‐25. The immunopositive material was located mainly on the plasmalemma. The nuclei were immunonegative, the cytoplasm was mildly immunopositive in several cells. Treatment of patients with dopamine agonists before surgery decreased markedly SNAP‐25 immunopositivity in 5/10 cases. In GH producing adenomas SNAP‐25 was seen in 5 cases. Immunopositivity was mild‐ moderate, membrane bound and cytoplasmic. Somatostatin analogs caused no marked reduction in immunopositivity (5 cases). Other adenoma types were practically immunonegative. Among human pituitary adenomas only PRL producing tumors release their secretory granules via exocytosis as was demonstrated by electron microscopy. This observation is concordant with our results. In dopamine agonist treated patients, decreased SNAP‐25 expression in PRL producing adenoma cells is consistent with reduction of blood PRL levels.

Abstract Eight surgical and one autopsy specimen of pituitary adenomas (six cases of Cushing's disease, two of Nelson's syndrome. and one of hypopituitarism) were studied by histochemical, immunohistocytological, and ultrastructural methods. Eight tumors showed the characteristic histochemical profile of corticotroph adenoma—amphophilic to basophilic, and periodic acid-Schiff-positive to some extent. In all tumors, immunohistochemical studies revealed adrenocorticotropic hormone (ACTH) and à-subunit in the cytoplasm of some adenoma cells. By electron microscopy, seven tumors were found to be monomorphous; six were typical corticotroph adenomas and one was a subtype II silent corticotroph adenoma. One unique lesion was bimorphous—i.e., composed of corticotrophs as well as cells resembling glycoprotein cells. Immunoelectron microscopy by the double-labeling immunogold technique, performed on one corticotroph adenoma, demonstrated the presence of ACTH and à-subunit not only within the same adenoma cells but also within the same secretory granules. The cytogenesis of ACTH à-subunit tumors, a rare form of plurihormonal adenoma. remains to be elucidated. The duration of disease associated with these tumors exceeded the duration in patients with ordinary corticotroph adenomas. Given the low frequency with which increases in serum à-subunit are detectable in patients with such tumors—13% in this series—hormone production is not recognized at preoperative evaluation.

Leptin is a key mediator in the maintenance of neuroendocrine homeostasis. Recently, leptin and leptin receptor expression were demonstrated in non-tumorous and adenomatous human pituitaries. This study was performed to determine the subcellular localization of leptin in human adenohypophyses ( n = 3) and in various types of pituitary adenoma ( n = 16). Immunoelectron microscopy showed leptin immunolabeling in most hormone-producing cells of the human non-tumorous adenohypophysis, but not in stellate cells. Labeling was noted over secretory granules. Immunocytochemistry using double labeling revealed leptin expression in GH-, ACTH-, TSH-, and FSH/LH-containing cells but not in PRL cells. The percentage of immunopositive cells and the intensity of immunostaining varied considerably among the various cell types. Immunoelectron microscopy with double gold labeling showed co-localization of leptin and adenohypophysial hormones in the same secretory granules. Among pituitary tumors, leptin immunolabeling was evident only in corticotroph adenomas. Compared to non-tumorous corticotrophs, leptin immunoexpression was less abundant in corticotroph adenomas. The presence of leptin and adenohypophysial hormones in the same secretory granules suggests that leptin is secreted concomitantly with various adenohypophysial hormones and that its release is under the control of hypothalamic stimulating and inhibiting hormones. (J Histochem Cytochem 48:1147–1152, 2000)

Objective. We investigated the correlation between immunohistochemical expression of the pituitary tumor transforming gene (PTTG) and pituitary adenoma subtype. Methods. Pituitary adenomas (n = 89) were stained for PTTG using the streptavidin—biotin—peroxidase complex method and a monoclonal PTTG antibody. Results. PTTG staining was found to be cytoplasmic with a pronounced paranuclear expression pattern. Reactivity was highest in growth hormone (GH) adenomas as compared with other tumors, including prolactin (PRL), follicle-stimulating hormone/luteinizing hormone/α subunit, as well as adrenocorticotrophic hormone—secreting adenomas. PRL adenomas exhibited the lowest expression levels. Among GH adenomas, untreated tumors demonstrated significantly higher PTTG levels than octreotide-treated examples. Although dopamine agonist—treated PRL adenomas tended to show lower expression levels, statistical significance was not reached. Conclusions. Our finding that PTTG was differentially expressed in pituitary adenoma subtypes suggests a cell-specific function for PTTG. Moreover, treatment of GH adenomas with somatostatin analogues lowered PTTG expression. Further investigation into mechanisms mediating cell-specific expression of PTTG is warranted.

Object The aim of this work was to investigate the immunohistochemical expression of nestin, a member of the intermediate filament family, in adenohypophysial vasculature during development and progression of pituitary infarction. Methods Forty-five nontumorous adenohypophyses and 34 pituitary adenomas of various types, all exhibiting acute or healing infarcts, were examined immunohistochemically using the streptavidin-biotin-peroxidase complex method. Results In both adenohypophyses and pituitary adenomas without infarction, nestin was expressed in only a few capillaries and endothelial cells. In acute infarcts without a vascular response, no nestin was demonstrable within necrotic capillaries (50 cases). In organizing infarcts, newly formed vessels spreading into necrotic zones showed nestin expression in all capillaries and practically every endothelial cell (25 cases). In the hypocellular, fibrotic scar phase, only a few vessels (4) were apparent, and immunoreactivity was focal and mild. Conclusions Nestin is strongly expressed in newly formed capillaries and is downregulated when infarcts transform to fibrous tissue. Nestin expression may provide valuable insight into the process of pituitary angiogenesis.

ABSTRACT OBJECTIVE To determine the clinical presentation, imaging characteristics, microscopic and ultrastructural characteristics, and treatment outcomes of patients with clinically silent pituitary corticotroph adenomas. METHODS All silent corticotroph adenomas diagnosed at the Mayo Clinic during the years 1975 through 1997 were selected from the files of the Mayo Tissue Registry. RESULTS We studied 23 cases, occurring in 16 male and 7 female patients (age range, 11–79 yr; mean age, 48 yr), who presented with headaches (50%), visual field defects (61%), extraocular muscle paresis (13%), hypopituitarism (26%), and galactorrhea/amenorrhea (43%/29% of the female patients). No patients exhibited clinical hypercortisolism. All tumors were macroadenomas (2.4 ± 0.8 cm; range, 1.5–4.0 cm) and exhibited suprasellar extension in 87% of the cases and hemorrhage, necrosis, and/or cystic changes in 61%. All tumors stained were variably periodic acid-Schiff-, adrenocorticotropic hormone-, and β-endorphin-positive, particularly Subtype I lesions. Ultrastructural classification was performed in 19 cases. In a comparison of Subtype I and II tumors, differences were observed with respect to sex (male/female, 1.4:1 versus 6:1), preoperative hyperprolactinemia (5 of 16 versus 0 of 6 cases), preoperative hypopituitarism (9 of 16 versus 5 of 7 cases), radiographic or gross invasion (7 of 16 versus 5 of 7 cases), and partial or total postoperative pituitary failure (6 of 16 versus 6 of 6 cases). The overall median postoperative follow-up period was 4.9 years (range, 0.3–16.6 yr); 54% of the patients had persistent or recurrent tumors. CONCLUSION Clinically silent corticotroph adenomas behave in an aggressive manner and are characterized by the following: lack of clinical signs or symptoms of Cushing's syndrome and normal cortisol levels; no or only minor elevations of serum adrenocorticotropic hormone levels; macroadenomas with hemorrhagic infarction; and presentation dominated by mass effect symptoms. The high persistence/recurrence rate underscores the need for long-term follow-up.