Analysis of endocrine active and clinically silent corticotropic adenomas by in situ hybridization.

The distribution of pro-opiomelanocortin (POMC) messenger RNA (mRNA) in 7 functional and 17 clinically silent corticotropic adenomas was analyzed by in situ hybridization (ISH) with 35S-labeled oligonucleotide probes using formalin-fixed paraffin-embedded tissue sections cut from blocks that were in storage between 1 to 14 years. All 7 functional adenomas and 4 subtype 1 tumors had detectable POMC mRNA, while 3 of 6 subtype 2 and 1 of 7 subtype 3 silent adenomas contained detectable POMC mRNA. In situ hybridization analysis with an 35S-labeled beta-actin probe showed a positive hybridization signal in 22 of 22 cases, indicating that the absence of detectable POMC mRNA in some adenomas was not due to loss of the mRNAs during processing of the tissues or because of the age of the embedded tissue blocks. Northern hybridization analysis with the oligonucleotide probes in 2 normal pituitaries and an adenoma causing Cushing's disease detected a 1.2-Kb mRNA in all three tissues, indicating that the oligonucleotide probes were very specific. These results indicate that subtype 1 silent adenomas and clinically active adenomas associated with Cushing's disease contain POMC mRNA that is readily detectable by ISH in routinely processed tissue specimens, while only a few of the subtypes 2 and 3 adenomas have POMC mRNA that can be detected in paraffin blocks with the oligonucleotide probes used in this study.     

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.     

Fine structure and morphogenesis of spironolactone bodies in the zona glomerulosa of the human adrenal cortex

Numerous spironolactone bodies have been detected in the zona glomerulosa cells of the adrenal cortex of a 36-year-old spironolactone-treated woman whose non-tumorous right adrenal gland was removed surgically because of primary hyperaldosteronism. Electron microscopy revealed spherical laminated whorls which consisted of a central core composed of an amorphous electron-dense material surrounded by numerous smooth-walled concentric membranes. Continuous with and deriving from the endoplasmic reticulum, they were present in viable cells and were not associated with ultrastructural features indicating cellular injury. Cytoplasmic inclusions similar to spironolactone bodies can be detected in other organs after the administration of various compounds. Thus, they can be regarded as neither specific to spironolactone treatment nor exclusively inducible in the zona glomerulosa of the adrenal cortex.     

Microvascular structural entropy: A novel approach to assess angiogenesis in pituitary tumors

Entropy, a measure of the degree of disorder in a system, has recently been used in different morphologic studies to quantify regularity. Our aims were (a) to study the structural organization of the microvascular bed in prolactin (PRL)-producing adenomas and carcinomas, the most vascularized of pituitary tumors, by assessing microvascular structural entropy (MSE), and (b) to determine whether the degree of disorder of the capillary bed correlates with tumor cell proliferation as estimated by MIB-1 labeling, microvessel density (MVD), the most widely used method of quantifying blood vessel formation, and various clinicopathologic parameters (gender, age, tumor size and invasiveness). The morphometric study demonstrated statistically significant differences in MIB-1 labeling, MVD, and MSE between PRL-producing adenomas and carcinomas. Unlike MIB-1 labeling index (PRL-producing adenomas 1.5±0.27; carcinomas 15.0±4.04) and MVD (PRL-producing adenomas 2.7±0.34; carcinomas 4.2±0.72), the MSE values were significantly higher in adenomas (171.5±25.37) than in carcinomas (67.9±17.45). These results indicate that PRL-producing carcinomas have a less chaotic distribution of vessels than benign adenomas. In contrast to a lack of correlation between, microvessel density and other morphometric parameters, a strong negative correlation was found between MSE and MIB-1 labeling index (r=0.511, p=0.003). It thus appears that regular, less chaotic microvascular geometry contributes to increased proliferative activity in PRL cell tumors. Analysis of MSE may provide an independent parameter of tumor behavior, and contributes to a better understanding of the role of microvasculature in pituitary tumor progression.