Differential diagnosis of pheochromocytomas and paragangliomas

Paragangliomas are of two types, sympathetic and parasympathetic, depending on the type of paraganglion in which they arise. The term pheochromocytoma is reserved for tumors arising in the adrenal medulla. These tumors are usually fairly easy to diagnose. However, several areas are the subject of debate, including the identification of malignant potential, the diagnosis of medullary hyperplasia, and the recognition of composite tumors. Some histologic features can cause problems in differential diagnosis. Paragangliomas may have spindle cell morphology or contain pigment, requiring distinction from mesenchymal tumors and melanoma, respectively. Extensive degenerative change in pheochromocytomas may mimic adrenal cortical tumors. This short review addresses the diagnosis of pheochromocytomas and paragangliomas and discusses useful approaches in the aforementioned problem areas.

Haploinsufficiency of steroidogenic factor-1 in mice disrupts adrenal development leading to an impaired stress response

Adrenal steroids are essential for homeostasis and survival during severe physiological stress. Analysis of a patient heterozygous for the steroidogenic factor-1 (SF-1) gene suggested that reduced expression of this nuclear receptor leads to adrenal failure. We therefore examined SF-1 heterozygous (+/-) mice as a potential model for delineating mechanisms underlying this disease. Here we show that SF-1 +/- mice exhibit adrenal insufficiency resulting from profound defects in adrenal development and organization. However, compensatory mechanisms, such as cellular hypertrophy and increased expression of the rate-limiting steroidogenic protein StAR, help to maintain adrenal function at near normal capacity under basal conditions. In contrast, adrenal deficits in SF-1 heterozygotes are revealed under stressful conditions, demonstrating that normal gene dosage of SF-1 is required for mounting an adequate stress response. Our findings predict that natural variations leading to reduced SF-1 function may underlie some forms of subclinical adrenal insufficiency, which become life threatening during traumatic stress.

[Hyperplasia of chromaffin cells in adrenocortical hyperplasia and adenoma]

OBJECTIVE

To study whether there is chromaffin cells hyperplasia in adrenocortical hyperplasia and adenoma.

METHODS

Chromaffin cells with chromogranin A were marked by immunohistochemistry method.

RESULTS

In 52 cases of adrenocortical hyperplasia and adenoma 3 were associated with eochromocyte hyperplasia and 5 with micro-pheochromocytoma. Six of the 8 cases were characterized by hypercortiso (or aldostero)-hypercatecholamine clinically.

CONCLUSIONS

Few cases of adrenocortical hyperplasia and adenoma may be associated with pheochromocytic hyperplasia and micro-pheochromocytoma, and may be characterized by symptoms of hypercortiso (or aldostero)-hypercatecholamine.

Sporadic bilateral adrenal medullary hyperplasia: apparent false positive MIBG scan and expected MRI findings

Adrenal medullary hyperplasia is a rare cause of clinical symptoms and biochemical findings identical to pheochromocytoma occurring mostly in multiple endocrine neoplasia patients. The scenario of positive MIBG scan, but no focal lesion found on CT and MRI led to diagnostic and management difficulties. Like pheochromocytoma, surgical excision can lead to clinical and biochemical recovery. We report this unusual case of sporadic bilateral adrenal medullary hyperplasia, with hypertension and biochemical abnormalities alleviated after surgical adrenalectomy. Based on T2 values reported in literature, high signal focal lesions may not appear on T2-weighted MRI images until development of frank pheochromocytoma. MIBG scan remains the most sensitive imaging modality for this condition.

Divergent differentiation in neuroendocrine tumors of the adrenal gland

Composite tumors of the adrenal medulla usually consist of pheochromocytoma admixed with ganglioneuroma or ganglioneuroblastoma. These neoplasms reflect phenotypic plasticity shown by primitive sympathetic cells and mature chromaffin cells in vitro. They may give rise to metastatic neuroblastoma in adults and may cause signs and symptoms attributable to both catecholamine and neuropeptide production. Schwann cells and sustentacular cells are typically numerous in these tumors but it is not known whether they are neoplastic. Immunohistochemical staining for catecholamine biosynthetic enzymes, secretory vesicle proteins and S-100 protein tends to recapitulate staining of the normal adrenal medulla or sympathetic ganglia. Sparsity of chromogranin A in the cell bodies of immature and mature neurons is a diagnostically useful characteristic.

Inhibition of apamin-sensitive K+ current by hypoxia in adult rat adrenal chromaffin cells

The effect of hypoxia on small-conductance Ca(2+)-activated K+ current was investigated in a study of adult rat adrenomedullary chromaffin cells (AMCs), which were maintained in short-term culture. The nystatin-perforated, whole-cell patchclamp technique was used to study the effect of hypoxia with minimum perturbation of the intracellular milieu. Under voltage-clamp conditions, acute hypoxia (P(O2) approximately equal to 25 mmHg) suppressed the whole-cell outward currents of more than half the AMCs (24/46). This suppression was eliminated after application of apamin (400 nM), a selective inhibitor of small-conductance Ca(2+)-activated K+ current (I(SK)(Ca)) (n=5), suggesting that an apamin-sensitive component of whole-cell currents is suppressed during hypoxia. In contrast to I(SK)(Ca), Ca2+ current (I(Ca)) (n=10) was not affected by hypoxia. Finally, under current-clamp conditions, hypoxia reversibly depolarized the resting membrane potential of adult AMCs (34/40). Apamin, however, eliminated the hypoxia-induced depolarization (400 nM) (7/8), suggesting that hypoxic depolarization is related to the suppression of I(SK(Ca). From the above results, we conclude that adult AMCs are sensitive to hypoxia, and that I(SK)(Ca) contributes to the hypoxia-induced suppression of whole-cell outward current and depolarization of the resting membrane potential in adult AMCs.

Organ-specific distribution of major histocompatibility antigens in rats

The present study systematically investigated the expression and distribution of the major histocompatibility complex (MHC) classes I and II in the rat. About 150 native tissue probes from eight adult Lewis rats were taken, representative for most organs, tissues, and the vascular system. MHC expression was analyzed by two monoclonal antibodies (mAb) generated against the non-polymorphic determinants of rat MHC class I (Ox-18) and class II (Ox-6). Immunoreactivities were compared to those of different endothelial (HIS52, TLD-3A12, Ox-43, REHA-1 antigen), histiocytic (ED1, ED2), B-cell (RLN-9D3), and T-cell (MRC Ox-52) markers. A nonspecific mAb (MR12/53) served as a negative control. Pretested concentrations on various tissues and the alkaline phosphatase-anti-alkaline phosphatase technique allowed semiquantitative evaluation of serial cryostat tissue sections. MHC class I expression was detected on most immunocompetent cells. Endothelial cells were stained heterogeneously along the vascular system and the organ-specific microcirculation. Furthermore, some organs showed staining of parenchymal cells. MHC class II was found on all immunocompetent cells positive for the B-cell marker and about 15% of cells positive for the histiocytic markers. Besides the well-known expression of MHC class II in the outer zone of the renal proximal tubule, further organ-specific cell forms were found positive. In conclusion, the present study outlines tissue-specific distribution of MHC I/ II and implies that each organ carries a variable immunologic burden that needs to be considered for any transplantation model.

Vitamin D3-induced proliferative lesions in the rat adrenal medulla

Adrenal medullary hyperplasia and pheochromocytomas are induced in rats by a variety of non-genotoxic agents, and we have hypothesized that these agents induce lesions indirectly by stimulating chromaffin cell proliferation. Vitamin D3, which has not been previously associated with adrenal medullary proliferative lesions, is the most potent in vivo stimulus to chromaffin cell proliferation yet identified. The present investigation utilized the vitamin D3 model to prospectively test the relationship between mitogenicity and focal proliferative lesions in the adrenal medulla and to determine early events in the pathogenesis of these lesions. Charles River Crl:CD BR rats were treated with 0; 5000; 10,000; or 20,000 IU/kg/day of vitamin D3 in corn oil (5 ml/kg) by oral intubation. Rats were killed after 4, 8, 12, or 26 weeks of treatment, following a final week of labeling with bromodeoxyuridine (BrdU) using a mini-pump. Adrenal sections were double-stained for BrdU and phenylethanolamine-N-methyl transferase (PNMT) to discriminate epinephrine (E) from norepinephrine (NE) cells or for vesicular acetylcholine transporter (VAchT) to identify cholinergic nerve endings. Vitamin D3 caused a 4-5-fold increase in BrdU labeling at week 4, diminishing to a 2-fold increase by week 26. An initial preponderance of labeled E cells gave way to a preponderance of labeled NE cells. By week 26, 17/19 (89%) animals receiving the 2 highest doses of vitamin D3 had focal adrenal medullary proliferative lesions, in contrast to an absence of lesions in control rats. The lesions encompassed a spectrum including BrdU-labeled "hot spots" not readily visible on H and E sections, hyperplastic nodules, and pheochromocytomas. Lesions were usually multicentric, bilateral, and peripheral in location, and almost all were PNMT-negative. The lesions were not cholinergically innervated, suggesting autonomous proliferation. Hot spots, hyperplastic nodules, and pheochromocytomas appear to represent a continuum rather than separate entities. Their development might involve selective responses of chromaffin cell subsets to mitogenic signals, influenced by both innervation and corticomedullary interactions. A number of non-genotoxic compounds that induce pheochromocytomas in rats are known to affect calcium homeostasis. The results of this study provide further evidence to support the hypothesis that altered calcium homeostasis is indirectly involved in the pathogenesis of pheochromocytomas, via effects on chromaffin cell proliferation.

Prompt recovery of damaged adrenal medullae induced by salinomycin

The morphologic changes in the adrenal medullae of rats treated with an ionophore antibiotic, salinomycin, are described. Male rats of approximately 7 wk of age were treated orally with a single dose of salinomycin at 80 mg/kg body weight. Following this treatment, the adrenal glands were examined, using immunohistochemistry, for neurofilament, laminin, fibronectin, and S-100 protein; the glands were also examined using transmission electron microscopy. One hour after the treatment, a karyopyknosis was observed in the clusters of affected chromaffin cells in which the neurofilament, laminin, and fibronectin were present. The lesions became progressively conspicuous between hours 5 and 10. Ultimately, the outcome was cell lysis. Five hours after salinomycin treatment, unaffected chromaffin cells strongly stained to tyrosine hydroxylase. At 10 hr, new chromaffin cells, which were irregular in shape with electron-dense cytoplasm (dark cell), that were strongly stained for tyrosine hydroxylase appeared at the basement membrane site of the necrotic clusters, and these cells contained very few immature catecholamine granules of less than 80 nm. At 17 hr, the catecholamine granules increased in number and size to about 200 nm. The newly formed chromaffin cells grew within the clusters to fill in the medulla by 24 hr, and cytoplasmic granules progressively increased in number and size. The interstitial tissue was seen to be edematous at 5 hr. New capillaries were found in the adrenal medullae of both control and salinomycin-treated rats. The protruding chromaffin cells (protruding cells), which we previously described in normal rats, were also observed in salinomycin-treated rats, which suggests that holocrine secretion is performed in the adrenal medullae. The results indicated that the rat adrenal medullae have the ability to make a rapid recovery after an insult by salinomycin.

Recommendations for reporting of tumors of the adrenal cortex and medulla. Association of Directors of Anatomic and Surgical Pathology

The Association of Directors of Anatomic and Surgical Pathology has developed recommendations for the surgical pathology report for common malignant tumors. The recommendations for tumors of the adrenal are reported herein.

[Status of the adrenal medulla in various forms of cardiomyopathy]

Adrenal medulla was studied quantitatively by a histofluorescent method and by that of Wood in 20 persons who had died at the age 35-50 years. The autopsy material was obtained from 11 dead bodies (control group--accident death) and those who had dilated and alcoholic cardiomyopathy (DCMP and ACMP, respectively). Catecholamine luminescence intensity (CLI) was higher in ACMP compared to control. On the contrary, CLI was low in chromaffin adrenal tissue in DCMP. The histofluorescent results corresponded to those obtained by a light microscopy by Wood method. The differences in results concerning catecholamines obtained in ACMP and DCMP were probably due to the differences in their activities in patients when they were alive (low in DCMP and high in ACMP).

Influences of long-term administration of 24R, 25-dihydroxyvitamin D3, a vitamin D3 derivative, in rats

In order to examine the influences by long-term feeding of 24R, 25 dihydroxyvitamin D3[24R, 25(OH)2D3], an active form of vitamin D, Wistar rats (14-week-old, male, 20 rats/group) were fed a powder diet containing 0 or 5 ppm 24R, 25(OH)2D3 for 57 weeks. Final body weights and total food consumption were comparable between the groups. Urinary calcium levels were significantly (p < 0.05 or 0.01) increased by the administration of 24R, 25(OH)2D3 at weeks 3, 22 and 56, although the levels of serum calcium did not differ between the groups at the termination of week 57. In the 24R, 25(OH)2D3 group, weights of the adrenals and femurs were significantly (p < 0.01) increased. Histopathologically, this was found due to thickening of cortical bone in the femurs, and medullary hyperplasia and pheochromocytoma of the adrenals. Immunohistochemically, proliferating cell nuclear antigen (PCNA)-labeling indices for intact adrenal medulla, medullary hyperplasia and pheochromocytoma in the 24R, 25(OH)2D3 group were respectively 1.82 +/- 1.21, 5.88 +/- 4.13 and 16, all higher than that for the adrenal medulla in the control group (0.87 +/- 0.67). These results indicate that 24R, 25(OH)2D3 at a dose with which serum calcium is not chronically increased causes thickening of the cortex of the femur, and development of adrenal proliferative lesions, suggesting that rats may be too sensitive for results to be relevant to human risk assessment.

Apoptosis in the adrenal gland of non-obese diabetic (NOD) mice

Apoptosis appears to play an important role in the development of diabetes in the non-obese diabetic (NOD) mouse. Since the autoimmune process leading to the manifestation of insulin dependent diabetes mellitus (IDDM) can also affect the sympathochromaffin system, we analyzed the role of apoptosis and infiltration of the adrenal medulla as features of this autoimmune process in parallel with the development of diabetes. Prediabetic and diabetic NOD mice aged 3 to 30 weeks were studied and compared with control mice. Apoptosis was assessed by in situ end-labeling method and ultrastructural analysis. Adrenals were screened for lymphocytic infiltration by conventional hematoxylin-eosin staining. Chromaffin cells were characterized by immunohistochemical staining against synaptophysin and tyrosine hydroxylase. Apoptotic nuclei were detected in all mice studied at a very low level, mainly occuring within the connective tissue between medulla and cortex. The maximum score was achieved at 3 weeks (1.91+/-0.48 apoptotic cells/1000 counted cells; n = 4). There was no significant difference between NOD mice and control mice. No correlation could be found between blood glucose levels and apoptosis. On the ultrastructural level, apoptotic cells presented typical features of apoptosis, i.e. condensed nuclei and cytoplasm. Neither in NOD mice nor in controls lymphocytic infiltration or fibrosis of the adrenal was detected. Even NOD mice with overt diabetes did not exhibit morphological signs of medullitis. In summary, no signs of immune destruction of the adrenal medulla in NOD mice aged 3 to 30 weeks could be detected.

[Adrenal medullary hyperplasia: a rare etiology of arterial hypertension--report of a case]

Adrenal medullary hyperplasia is often misdiagnosed. The clinical features may resemble those of pheochromocytoma, with paroxysmal hypertension and elevated urinary catecholamine and metanephrine levels. Pathologic study shows diffuse or nodular adrenal medullary hyperplasia, determined by morphometric analysis: increased adrenal gland weight, increased relative medullary volume, increased relative medullary weight, decreased cortico-medullary ratio. Adrenal medullary hyperplasia may be primary or sporadic, but is often associated with multiple endocrine neoplasia (MEN) type II.

BCL-2 expression and inhibin-A in adrenal neoplasms: a comparative study

Differential diagnosis between adrenal cortical and adrenal medullary lesions may be difficult in many cases. Different immunohistochemical, histochemical tools as well as ultrastructural diagnostic techniques have been employed to aid in differentiating between these lesions. Recently, both inhibin-A and BCL-2 have been shown to stain selectively adrenal cortical tissue and its derived neoplasms but not adrenal medulla or pheochromocytomas. In this study we compared the staining reactions of inhibin-A and BCL-2 in cases of adrenal cortical adenomas and carcinomas as well as pheochromocytomas. We found that both inhibin-A and BCL-2 stained cortical derived tissues, but not medullary derived tissues. Staining intensity for inhibin-A was significantly weaker than for BCL-2. We found that fixation techniques may influence the staining reactivity, as some cases did not immunoreact with any of the antibodies. We conclude that both inhibin-A, and, preferentially, BCL-2 are useful additions to a staining protocol to help in the differential diagnosis of cortical and medullary neoplasms.

[Surgical treatment of adrenal gland tumors]

The data on surgical treatment of 146 patients with adrenal gland malignancies as well as literature on the problem are discussed.

Optimal conditions to induce rat adrenal medullary changes, such as pheochromocytoma, by nicotine

BACKGROUND

Nicotine-induced adrenal medullary hypertrophy in rats has been suggested to be a model for pheochromocytoma. Study conditions for proving such an assertion, however, have not been optimized.

METHODS

Studies on strain difference, dose dependency, and the time course of catecholamine metabolism in response to nicotine treatment were conducted. Under the putative optimal experimental conditions, metabolic and histologic changes in the adrenal medulla were investigated.

RESULTS

Male Wistar rats treated with a maximum dose of 4 mg/kg per day of nicotine for 9 weeks, including a 2-week lead-in period, developed highly consistent changes in the adrenal medulla. Concerning metabolic indices, the norepinephrine content of the adrenal and the urinary excretion of epinephrine and metanephrine were significantly elevated. Hyperplastic and hyperactive states of the adrenal medulla were also indicated by a morphometric analysis on electron microscopic figures. These showed an enlarged cytoplasmic area, the development of a rough-surfaced endoplasmic reticulum, and an increased number and density of intracellular catecholamine granules. The metabolic changes were found to reverse 3 weeks after the cessation of nicotine administration.

CONCLUSION

These results provide better-defined experimental conditions for an animal model of pheochromocytoma.

["Black adenoma" associated with medullary nodular hyperplasia in the ipsilateral adrenal gland. Case report and review of the literature regarding "mixed" cortico-medullary pathology]

BACKGROUND

Pigmented or "black" cortical adenoma is a rare variant of the compact or eosinophilic cell type of adrenal gland cortical adenoma. Usually it is non functioning so representing an incidental finding at autopsy, but rare cases producing Cushing's syndrome or hyperaldosteronism have been reported. The simultaneous occurrence of a cortical adenoma and pheochromocytoma in the ipsilateral adrenal gland is an extremely rare event, which has been so far described only seven times with the cortical adenoma always being of the usual yellow or clear cell type. So far no case of "black adenoma" associated with a proliferative condition of the ipsilateral adrenal medulla has ben described.

CASE REPORT

A case of functioning pigmented ("black") cortical adenoma in a male patient affected by Cushing's syndrome associated with asymptomatic medullary nodular hyperplasia in the ipsilateral adrenal gland is described. The results of light microscopy, histochemistry, immunohistochemistry, and electron microscopy studies are presented. It is worthy of note the finding of two types of pigment granules (lipofuscin type, neuromelanin type) observed at elecatron microscopy.

CONCLUSIONS

The authors underline the difficulty of classifying adrenal medullary nodules and the arbitrarity usually adopted in separating nodular adrenal medullary hyperplasia from early neoplasia (pheochromocytoma). Thus nodular medullary hyperplasia in this case could also be interpreted as an early neoplastic condition. The case herein presented is the first report of a combined cortico-medullary proliferative process in which a "black" adenoma is involved.

Immunological responses to injury and grafting in the central nervous system of nonhuman primates

Allogeneic transplantation for the therapy of human Parkinson's disease is being considered as a viable approach at several clinical centers worldwide. As an attempt to understand the basic biology of central nervous system (CNS) transplantation, our laboratory has developed an experimental nonhuman primate model for human Parkinson's disease and carried out preliminary studies directed at evaluating the potential pathology at the graft site. In addition, studies have been conducted to examine whether such transplantation procedures lead to specific and/or nonspecific immunologic sensitization of the host or results in generalized immunosuppression. Groups of rhesus macaques (Macaca mulatta) were either controls operated (n = 6), autografted with adrenal medullary and peripheral nerve tissue (n = 3), or allografted with fetal mesencephalic tissue (n = 6). Immunohistological studies demonstrated the presence of mononuclear cell infiltrates as early as 1 wk and up to 1 yr postoperatively, although the frequency of the infiltrating cells declined with time. The infiltrates consisted of variable numbers of cells which express CD2+, CD3+, CD4+, CD8+, CD19+, CD22+, CD25+, and CD68+. There appeared to be no difference in the frequency, kinetics, or phenotype of the infiltrating cells in operative controls compared with recipients of auto- or allografts. Tissue sections obtained postoperatively showed low levels of major histocompatibility complex (MHC) Class I antigens and no detectable level of MHC-Class II antigens in neural tissue. A small aliquot of tissue from the operative site was placed in vitro with media containing interleukin-2 (IL-2), which led to the exudation and growth of mononuclear cells that were predominantly CD4+ cells. Phenotypic studies of peripheral blood mononuclear cells (PBMC) from operative controls, auto- and allograft recipient monkeys performed at varying time periods postoperatively failed to show differences in the frequencies of subsets of T-cells, B-cells, NK-cells, or monocytes. Studies on aliquots of the same PBMC failed to show major functional differences in NK-cells, LAK cells, or response to polyclonal mitogens. Finally, recipients of allogeneic mesencephalic grafts failed to show evidence of donor-specific humoral or cellular sensitization. These data indicate that transplantation of autograft adrenal or allograft fetal mesencephalic tissues in the CNS of nonhuman primate did not induce detectable donor-specific sensitization nor nonspecific immunosuppression.

Class III beta-tubulin isotype (beta III) in the adrenal medulla: III. Differential expression of neuronal and glial antigens identifies two distinct populations of neuronal and glial-like (sustentacular) cells in the PC12 rat pheochromocytoma cell line maintained in a Gelfoam matrix system

BACKGROUND

The rat PC12 pheochromocytoma cell line provides an established system for the study of neuronal differentiation. To our knowledge, glial differentiation has not been reported in this cell line.

METHODS

We have studied, by immunohistochemistry and immunoblotting, the presence of neuronal cytoskeletal antigens [class III beta-tubulin isotype (beta III), microtubule associated proteins MAP2, MAP1B and tau, and different neurofilament (NF) protein components], and synaptophysin in comparison with the glial fibrillary acidic protein (GFAP) and S-100 protein in the PC12 cell line. In three different experiments, PC12 cells were maintained in a three-dimensional gelatin foam (Gelfoam) matrix system for up to 34 days with and without treatment with 1 mM dibutyryl cyclic (dc)AMP. Immunohistochemistry was performed on explants ranging from 2 to 32 days-in vitro, which were fixed in either Bouin's solution, 70% ethanol, or 10% neutral-buffered formalin and embedded in paraffin. Immunoblotting was performed on Gelfoam explants with a panel of antibodies against all aforementioned neuronal and glial markers. Additional immunoblot experiments using anti-GFAP and anti-beta III monoclonal antibodies in cell suspensions and homogenates from PC12 monolayer cultures were carried out to compare growth conditions in relation to the expression of these proteins.

RESULTS

Beta III and MAP2 were demonstrated by immunohistochemistry and immunoblotting of PC12 explants maintained for up to 32 days in Gelfoam matrices with and without treatment with dcAMP. Intense filamentous and granular beta III staining of PC12 cells was observed in dcAMP-treated cultures concomitant with neuronal morphologic alterations (neuritogenesis and ganglionic phenotype). In untreated cultures, beta III staining was present in less differentiated cells, as well in cells undergoing neuritic development. The neuronal phenotype of PC12 cells was confirmed by staining for MAP2, tau, and NF proteins, as well as for synaptophysin. The presence of beta III, MAP2, MAP1B, tau, and NF proteins was confirmed by immunoblotting. Clusters of GFAP-positive and S-100 protein-positive spindle cells, phenotypically distinct from the chromaffin-like or neuronal cells, were demonstrated in Gelfoam explants at 5-30 days in vitro. In 30-day-old cultures treated with dcAMP, there was strong filamentous GFAP and diffuse S-100 protein staining in an increased number of sustentacular-like PC12 cells. GFAP staining was corroborated by immunoblotting of explants maintained under identical conditions in vitro. In contrast, immunoblots performed on homogenates from PC12 suspension and monolayer cultures were GFAP-negative.

CONCLUSIONS

Neuronal and glial-like, presumed sustentacular, phenotypes were demonstrated in PC12 cells grown in Gelfoam matrices with and without treatment with dcAMP for up to 34 days. To our knowledge, the occurrence of glial differentiation in the PC12 line is a hitherto unreported finding. Adult rat medullary sustentacular cells are known to express S-100 and GFA proteins (Suzuki and Kachi, Kaibogaku Zasshi-Anat 70(2): 130-139, 1995), and the organ culture system employed in our study may well have favored this direction of differentiation.

Mitotane (o,p'-DDD) resistance in a dog with pituitary-dependent hyperadrenocorticism and phaeochromocytoma

A dog was presented with a 2 year history of polyuria and polydipsia due to pituitary-dependent hyperadrenocorticism. A low-dose dexamethasone suppression test and measurement of plasma ACTH concentration confirmed the diagnosis. Treatment was instituted with mitotane at 44 mg/kg/day and then 88 mg/kg/d without complete resolution of signs. The dog collapsed with signs consistent with liver disease and was euthanased. Necropsy revealed a phaeochromocytoma of the left adrenal medulla with extensive metastases to the liver. A chromophobe adenoma of the pars intermedia of the pituitary was found.

Iodine-131 MIBG imaging in multiple endocrine neoplasia type 2B

A 16-year-old boy had a swollen neck that was a result of multiple endocrine neoplasia Type 2B (MEN 2B). CT revealed bilateral thyroid tumors, swelling of right cervical lymph nodes, and slight enlargement of the right adrenal gland. I-131 metaiodobenzylguanidine (MIBG) scintigraphy demonstrated increased uptake in the right adrenal gland and the left thyroid tumor, but no abnormal uptake in the right thyroid tumor and the right cervical lymph nodes. Postoperative pathologic findings were consistent with the diagnosis of right adrenal medullary hyperplasia, which is a precursor of pheochromocytoma. In patients with MEN 2B, I-131 MIBG scintigraphy in conjunction with CT of the adrenal glands should be performed to determine the disease stage of the adrenal medullae. In the cervical region, the diagnosis was medullary thyroid carcinoma (MTC) in both thyroid tumors and metastases in the right cervical lymph nodes. The right MTC was more aggressive than the left MTC. It is interesting that not all sites of known MTC take up I-131 MIBG to the same degree.