A 2-year dose-response study of lesion sequences during hepatocellular carcinogenesis in the male B6C3F(1) mouse given the drinking water chemical dichloroacetic acid.

Dichloroacetic acid (DCA) is carcinogenic to the B6C3F(1) mouse and the F344 rat. Given the carcinogenic potential of DCA in rodent liver and the known concentrations of this compound in drinking water, reliable biologically based models to reduce the uncertainty of risk assessment for human exposure to DCA are needed. Development of such models requires identification and quantification of premalignant hepatic lesions, identification of the doses at which these lesions occur, and determination of the likelihood that these lesions will progress to cancer. In this study we determined the dose response of histopathologic changes occurring in the livers of mice exposed to DCA (0.05-3.5 g/L) for 26-100 weeks. Lesions were classified as foci of cellular alteration smaller than one liver lobule (altered hepatic foci; AHF), foci of cellular alteration larger than one liver lobule (large foci of cellular alteration; LFCA), adenomas (ADs), or carcinomas (CAs). Histopathologic analysis of 598 premalignant lesions revealed that (a)) each lesion class had a predominant phenotype; (b)) AHF, LFCA, and AD demonstrated neoplastic progression with time; and (c)) independent of DCA dose and length of exposure effects, some toxic/adaptive changes in non-involved liver were related to this neoplastic progression. A lesion sequence for carcinogenesis in male B6C3F(1) mouse liver has been proposed that will enable development of a biologically based mathematical model for DCA. Because all classes of premalignant lesions and CAs were found at both lower and higher doses, these data are consistent with the conclusion that nongenotoxic mechanisms, such as negative selection, are relevant to DCA carcinogenesis at lower doses where DCA genotoxicity has not been observed.

Pituitary carcinoma: an ultrastructural study of eleven cases.

Pituitary carcinomas are very rare. Defined as adenohypophysial tumors that undergo craniospinal and/or systemic metastasis, most are PRL- or ACTH-producing. Their ultrastructural features, particularly relative to benign adenomas of similar functional type, have not been sufficiently explored. Eleven cases of immunohistochemically characterized pituitary carcinoma with documented cerebrospinal and/or systemic metastases were collected from various institutions and studied by transmission electron microscopy. The tumors were surgically removed from 7 women and 4 men ranging in age between 28 and 74 years (mean, 50 years). All were endocrinologically functioning. Six tumors secreted PRL; three were ACTH-producing; one each was GH/PRL- and TSH-producing. The patients with the ACTH-producing tumors had all presented with Cushing's disease and two of them had undergone adrenalectomy (Nelson syndrome). In most cases significant cellular atypia and mitotic activity were observed. In terms of morphologic features of functional differentiation, electron microscopy revealed that in 9 cases the tumor cells maintained at least some ultrastructural markers of their basic phenotype. A unique feature in 2 ACTH carcinomas was the variable admixture of smooth endoplasmic reticulum with intermediate (cytokeratin) filaments. In 2 cases, both PRL-producing carcinomas, the cell type comprising the tumor could not be identified on an ultrastructural basis alone. Ultrastructural investigation of pituitary carcinomas confirms their endocrine nature and, in most but not all cases, reveals their functional differentiation. Despite the diagnostic utility of electron microscopy in the assessment of these rare tumors, the distinction of pituitary carcinoma from pituitary adenoma cannot be firmly made on ultrastructural grounds alone.

Effects of growth hormone-releasing hormone (GHRH) on densely granulated somatotroph adenomas and sparsely granulated somatotroph adenomas in vitro: a morphological and functional investigation.

The effects of growth hormone-releasing hormone (GHRH) were studied on densely granulated somatotroph adenoma cells and sparsely granulated somatotroph adenoma cells in culture by measuring release of growth hormone (GH) as well as ultrastructural morphometrical parameters and comparing them with those of control adenoma cells. Both types of adenoma cells cultured with GHRH showed similar increases of GH release into culture media and exhibited similar increases in cytoplasmic volume densities (CVD) of endoplasmic reticulum and Golgi apparatus and decreases in CVD of secretory granules and secretory granule diameter. These results indicate that (1) both types of somatotroph adenoma cells react similarly to GHRH stimulation, despite their morphologic differences, and (2) GHRH stimulates GH synthesis as well as GH release by somatotroph adenoma cells.

Papillary oncocytoma of the eyelid. A previously undescribed tumor of apocrine gland origin.

Oncocytomas are uncommon tumors arising within the ductular cell lining of glandular structures. The oncocytic cells are characteristically large and rich in eosinophilic cytoplasm. Electron microscopic studies show densely packed mitochondria with irregular, whorled, or fragmented cristae. Ocular adnexal oncocytomas have been reported to arise in the caruncle, lacrimal gland, and lacrimal sac. The authors recently encountered an oncocytic tumor occurring in a most unusual location, the skin of the medial lid margin and commissure. Microscopically, the lesion was papillary and cystic in architecture, and arose from an adjacent apocrine gland of the eyelid margin (gland of Moll). Electron microscopic studies showed that the tumor cells were packed with malformed mitochondria to the exclusion of other organelles. This is the first report documenting an oncocytic lesion arising in the skin from an adnexal gland.

Light and electron microscopical morphometry of pituitary adenomas in hyperprolactinemia.

Two highly differentiated acidophil prolactin-cell adenomas with hyperprolactinemia (group I), 8 large cell chromophobe adenomas with hyperprolactinemia (group II), and 2 small cell chromophobe adenomas (group III), one of which was combined with hyperprolactinemia, were studied immunohistologically. Morphometry was performed on the light- and electron microscopical level. The 11 active adenomas were immunohistologically positive for prolactin, the 12th adenoma with normal prolactin plasma level was negative for prolactin. Light microscopical morphometry displayed significantly more cells of smaller size in the "small cell chromophobe" adenomas, whereas the large cell chromophobe adenomas and the highly differentiated prolactin cell adenomas were not different. Ultrastructural morphometry demonstrated significant differences between highly differentiated prolactin cell adenomas (group I), and large cell chromophobe adenomas (group II). The latter contain smaller "relative volumes" of nucleoli and of secretory granules, whereas the rough endoplasmic reticulum, the Golgi fields and the nuclei were not different. Comparison of large cell chromophobe adenomas (group II), and small cell chromophobe adenomas (group III) revealed significantly larger relative volumes of nuclei and of mitochondria but smaller volumes of rough endoplasmic reticulum and of Golgi fields in the small cell chromophobe adenomas. Significant differences between the active and the inactive adenoma of small cell chromophobe type in the group III were not found. In spite of the low quantity of small cell chromophobe adenomas and of acidophil prolactin cell adenomas, our data demonstrate that there exist distinct and significant light microscopical and ultrastructural differences between the three adenoma types.(ABSTRACT TRUNCATED AT 250 WORDS)

Electron dense mitochondrial inclusions in a pituitary oncocytoma.

A 65-year-old man had a pituitary adenoma with a large expansion of the sella turcica; computerized tomography demonstrated suprasellar extension. The tumor, removed surgically, was diagnosed as nonsecretory partly chromophobic, partly acidophilic adenoma by light microscopy and immunocytology. Electron microscopic investigation revealed a pituitary oncocytoma with an unusual mitochondrial abnormality. Some mitochondria harbored single or multiple electron dense bodies which were also found in the cytoplasm as well as in the extracellular space. It appears that these bodies were originally formed in the mitochondria, then extruded into the cytoplasm and subsequently to the extracellular space.

Pituitary adenomas producing growth hormone, prolactin, and one or more glycoprotein hormones: a histologic, immunohistochemical, and ultrastructural study of four surgically removed tumors.

The morphologic features of four pituitary adenomas, removed from 2 men and 2 women between 31 and 62 years of age, are reported. The tumors contained growth hormone (GH), prolactin (PRL), and one or more glycoprotein hormones--usually thyrotropin (TSH). Three tumors were associated with acromegaly and one with hyperprolactinemia. Hyperthyroidism was not evident in any of the patients. In the tumors of acromegalic subjects, GH-containing cells were the most numerous, whereas PRL cells were dominant in the adenoma accompanied by hyperprolactinemia. Electron microscopy revealed plurimorphous tumors comprised of various proportions of morphologically different cell types: densely granulated GH cells, TSH-like cells, and the less common mammosomatotrophs and PRL cells. It is suggested that pituitary adenomas producing GH, PRL, and glycoprotein hormones derive from the same precursor; their immunocytochemical profile, fine structural appearance, and endocrine function may depend on the degree and direction of the cellular differentiation.

Immunohistochemical and immunoelectron-microscopic study of pituitary adenomas associated with Cushing's disease. A report of 13 cases.

Thirteen pituitary adenomas were removed from patients with Cushing's disease by the transphenoidal route. All cases demonstrated a typical histochemical and ultrastructural pattern. Immunocytochemical study by means of the immunoperoxidase technique and light or electron microscopy demonstrated 1-24/1-39 adrenocorticotropic hormone (ACTH) in all cases, lipotropin/melanotropin (beta-LPH/beta-MSH) in 10 cases, beta-endorphin in 8 cases, and an absence of calcitonin in all cases. In addition, in 2 cases tumor tissue contained a few antiprolactin immunoreactive cells. These ACTH, beta-LPH, and beta-endorphin immunoreactivities may reflect either the peptides themselves or their precursors or intermediate products. The authors also suggest a possible intermediate-lobe-like processing of beta-LPH leading to beta-endorphin production, which may act on PRL cells. In addition, no positive arguments for the existence of a common precursor for calcitonin and ACTH could be provided from this study.

[Functional morphology of pituitary adenoma in acromegaly]. / Funktsional'naia morfologiia adenomy gipofiza pri akromegalii.

Twenty-one pituitary adenomas removed from patients with acromegaly were studied electron microscopically. In 9 cases the tumors underwent immunohistochemical analysis by Coons' indirect immunofluorescent technique. Before the operation, all the patients were found by radioimmunoassay to have concentrations of pituitary hormones in the blood serum. A clinico-morphological analysis performed showed that in all cases of acromegaly pituitary adenoma consisted of somatotropocytes differing by the degree of cell granulation. The concentration of the somatotropic hormone (STH) in the blood serum of the patients did not depend on the intensity of the ultrastructural signs of the secretory activity of the cells. In 4 adenomas, a positive immunohistochemical reaction to two hormones, STH and prolactine, was demonstrated.

Pituitary adenomas with hyperfunction of TSH. Frequency, histological classification, immunocytochemistry and ultrastructure.

In a collection of 564 surgically removed pituitary adenomas, 4 cases werefound to have had elevated TSH plasma levels. One of these tumors )(case 1) could be classified as a highly differentiated mucoid TSH cell adenoma presenting histochemical reactions typical of, as well as electron microscopical features identical to, normal TSH cells. Immunoenzymatic studies failed to dfemonstrate TSH in the tumor cells. Two further adenomas (case 2 and 3) were similarly structured in many areas, but showed regions of poorer differentiation in which distinct pleomorphism, irregular secretory granules, increased numbers of ribosomesand a well developed rough endoplasmic reticulum were present. In 10% of the tumor cells GH could be demonstrated immunoenzymatically, but there was no TSH. The fourth adenoma was an undifferentiated acidophilic adenoma showing pleomorphic cells having slight acidophil and partly mucoid granulations. The ultrastructure showed convoluted nuclei, increased numbers of free ribosomes as well as abundant rough endoplasmic reticulum and secretory granules which were differentin size and number but distinctly of the TSH cell type. Immunoenzymatically, TSH was found in some cells, with GH in more cells. Endocrinologically, elevated levels of GH were measured in cases 2, 3 and 4 with LH being increased in case 1. Clinical and morphological correlations are discussed.

Light- and electron-microscopic features of an endocrinologically active pituitary adenoma cultured in vitro.

A pituitary adenoma from an acromegalic female patient has been studied in cell cultures. Two populations of parenchymal cells, i.e., elongated shapes and big pale forms with irregular outlines, were distinguished light-microscopically. Ultrastructurally, three types of cells were found. Two of them contained secretory granules in varying numbers and sizes. Based on the proportion of the various cellular elements these cells were considered as counterparts of the elongated shapes being responsible for the GH secretion at different rates. The third cell type with very few secretory granules was identified with the big pale forms. Presumably, they could be exhausted GH-secreting cells. Besides fine structural characterisation, cultured cells of endocrinologically active human pituitary adenomas offer suitable models for studying some phases of exocytosis and membrane retrieval.

The ultrastructure of the adenomatoid odontogenic tumor.

An adenomatoid odontogenic tumor (AOT) which occurred in the maxilla of an 8-year-old boy was studied by the light and electron microscopy. The tumor was found to contain cells resembling preameloblasts, the stratum intermedium, and the stellate reticulum, suggesting its origin from the enamel organ, in agreement with previous reports. Characteristic ductlike structures are thought to be formed as a result of secretory activity of the tumor cells, rather than degeneration. Duct-lining cells ultrastructurally similar to preameloblasts were found to contain electron-dense granules. These granules are believed to play a role in secretion by tumor cells, a concept not previously considered. The results of previous ultrastructural studies of the AOT are reviewed and summarized.

Acidophil stem cell adenoma of the human pituitary: clinicopathologic analysis of 15 cases.

In material of 347 surgically removed pituitary adenomas, 15 tumors (4.3%) were diagnosed as acidophil stem cell adenomas. These are immature neoplasms, assumed to derive from the common progenitor of growth hormone and prolactin cells, and usually containing both hormones by the immunoperoxidase technique. Clinically, they are regularly associated with hyperprolactinemia. Some patients may exhibit physical stigmata of acromegaly without biochemical evidence of the disease ("fugitive acromegaly"). The entity is also characterized by (1) relatively short clinical history; (2) large (grade III--IV), locally invasive adenoma, and (3) relatively low hormonal activity. By electron microscopy, these tumors are unicellular with immature cytoplasm, exhibiting some features of adenomatous growth hormone and prolactin with immature cytoplasm, exhibiting some features of adenomatous growth hormone and prolactin cells and frequently mitochondrial abnormalities as well. They are more aggressive than the well-differentiated adenomas of the "acidophil" cell line--a fact to be considered in postoperative management.

Growth hormone-producing pituitary adenoma with giant secretory granules.

Unusually large, oval and pleomorphic secretory granules were noted by electron microscopy in an acidophilic adenoma of the pituitary. The tumor, which was removed by surgery from a 42-year-old woman with elevated blood growth hormone levels and the clinical features of acromegaly, was found to contain growth hormone by the immunoperoxidase technique. This ultrastructural abnormality of secretory granules was not reported so far and was not seen among the 58 cases of growth hormone-producing adenomas investigated in our laboratory. The present case clearly shows that the cytogenesis and cellular composition of pituitary adenomas cannot be determined by solely examining the size and shape of secretory granules.