Clonality as expression of distinctive cell kinetics patterns in nodular hyperplasias and adenomas of the adrenal cortex

Mouse models of adrenocortical tumors

The molecular basis of the organogenesis, homeostasis, and tumorigenesis of the adrenal cortex has been the subject of intense study for many decades. Specifically, characterization of tumor predisposition syndromes with adrenocortical manifestations and molecular profiling of sporadic adrenocortical tumors have led to the discovery of key molecular pathways that promote pathological adrenal growth. However, given the observational nature of such studies, several important questions regarding the molecular pathogenesis of adrenocortical tumors have remained. This review will summarize naturally occurring and genetically engineered mouse models that have provided novel tools to explore the molecular and cellular underpinnings of adrenocortical tumors. New paradigms of cancer initiation, maintenance, and progression that have emerged from this work will be discussed.

Adrenocortical adenomas with regression and myelolipomatous changes: urinary steroid profiling supports a distinctive benign neoplasm

BACKGROUND

Adrenocortical neoplasms are classically divided into adenomas (ACA) and carcinomas (ACC). Heterogeneous appearance and greater size are criteria to suggest malignancy, along with the urinary steroid profile (USP). The presence of regression and myelolipomatous changes in adenomas (ACA-RML) can contribute to confusion with ACC and its USP remains unknown.

OBJECTIVE

To evaluate the features of ACA-RML in comparison with other adrenocortical neoplasms.

METHODS

We selected consecutive ACA (11), ACA-RML (7) and ACC (13) cases for which USP analysis was performed before surgery and tissue was available for histological evaluation (King's College Hospital, 2005-2012). Cases were classified according to WHO and Armed Forces Institute of Pathology criteria. USPs were obtained by gas chromatography/mass spectrometry. Total excretion of individual steroids and indices (sums and ratios chosen to reflect steroid metabolic activity) were compared between ACA-RML, ACA and ACC.

RESULTS

In comparison with ACA, tumours in ACA-RML were significantly larger (8·5 ± 2·4 vs 3·5 ± 1·0, P = 0·002), presented in older patients and showed relatively higher incidence in males. Mitotic figure counts were significantly lower (0·39 ± 0·04 vs 0·93 ± 0·11 in ACA, P = 0·001) and revealed higher frequency of apoptotic cells (100% vs 9% in ACA, P = 0·001). The USP of ACA-RML showed no diagnostic features of ACC. No differences from ACA were significant, but there was a tendency towards lower dehydroepiandrosterone DHA and DHA metabolites.

CONCLUSIONS

ACA-RML reveals distinctive histological features and lack of USP markers of malignancy. More cases of this rare tumour may confirm differences from ACA in steroid excretion. It is important to recognize ACA-RML because its size and heterogeneous appearance raise the possibility of ACC.

Tumor heterogeneity: mechanisms and bases for a reliable application of molecular marker design

Tumor heterogeneity is a confusing finding in the assessment of neoplasms, potentially resulting in inaccurate diagnostic, prognostic and predictive tests. This tumor heterogeneity is not always a random and unpredictable phenomenon, whose knowledge helps designing better tests. The biologic reasons for this intratumoral heterogeneity would then be important to understand both the natural history of neoplasms and the selection of test samples for reliable analysis. The main factors contributing to intratumoral heterogeneity inducing gene abnormalities or modifying its expression include: the gradient ischemic level within neoplasms, the action of tumor microenvironment (bidirectional interaction between tumor cells and stroma), mechanisms of intercellular transference of genetic information (exosomes), and differential mechanisms of sequence-independent modifications of genetic material and proteins. The intratumoral heterogeneity is at the origin of tumor progression and it is also the byproduct of the selection process during progression. Any analysis of heterogeneity mechanisms must be integrated within the process of segregation of genetic changes in tumor cells during the clonal expansion and progression of neoplasms. The evaluation of these mechanisms must also consider the redundancy and pleiotropism of molecular pathways, for which appropriate surrogate markers would support the presence or not of heterogeneous genetics and the main mechanisms responsible. This knowledge would constitute a solid scientific background for future therapeutic planning.

Heterogeneous topographic profiles of kinetic and cell cycle regulator microsatellites in atypical (dysplastic) melanocytic nevi

Atypical (dysplastic) melanocytic nevi are clinically heterogeneous malignant melanoma precursors, for which no topographic analysis of cell kinetic, cell cycle regulators and microsatellite profile is available. We selected low-grade atypical melanocytic nevi (92), high-grade atypical melanocytic nevi (41), melanocytic nevi (18 junctional, 25 compound) and malignant melanomas (16 radial growth phase and 27 vertical growth phase). TP53, CDKN2A, CDKN1A, and CDKN1B microsatellite patterns were topographically studied after microdissection; Ki-67, TP53, CDKN2A, CDKN1A, and CDKN1B expressions and DNA fragmentation by in situ end labeling for apoptosis were topographically scored. Results were statistically analyzed. A decreasing junctional-dermal marker expression gradient was observed, directly correlating with atypical melanocytic nevus grading. High-grade atypical melanocytic nevi revealed coexistent TP53-CDKN2A-CDKN1B microsatellite abnormalities, and significantly higher junctional Ki67-TP53 expression (inversely correlated with CDKN1A-CDKN1B expression and in situ end labeling). Malignant melanomas showed coexistent microsatellite abnormalities (CDKN2A-CDKN1B), no topographic gradient, and significantly decreased expression. Melanocytic nevi and low-grade atypical melanocytic nevi revealed sporadic junctional CDKN2A microsatellite abnormalities and no significant topographic kinetic differences. High-grade atypical melanocytic nevi accumulate junctional TP53-CDKN1A-CDKN1B microsatellite abnormalities, being progression TP53-independent and better assessed in the dermis. Melanocytic nevi and low-grade atypical melanocytic nevi show low incidence of microsatellite abnormalities, and kinetic features that make progression unlikely.

Progress in primary aldosteronism: present challenges and perspectives

Primary Aldosteronism (PA) is a disorder of the adrenal zona glomerulosa (ZG) in which aldosterone secretion is increased and is relatively autonomous of normal regulatory mechanisms. A recent conference in Munich organized by Prof. Reincke addressed advances and challenges related to the screening, diagnosis, and identification of uni- and bilateral involvement of the diseased adrenal of PA. Some infrequently addressed issues are described herein. We postulate that most cases of PA are due to the activation by unknown mechanisms of subset of cells resulting in the formation of a multiple foci or nodules of hyperactive zona glomerulosa cells. This implies that one or several yet unidentified stimuli can drive aldosterone overproduction, as well as the proliferation of aldosterone-producing cells. Current diagnostic procedures allow to determine whether inappropriate aldosterone production is driven by one or both adrenal glands and thus to establish optimal treatment.

Coexistent intraurothelial carcinoma and muscle-invasive urothelial carcinoma of the bladder: clonality and somatic down-regulation of DNA mismatch repair

Muscle-invasive urothelial carcinomas are heterogeneous neoplasms for which the clonal relationship with low-grade urothelial dysplasia and carcinomas in situ remains unknown, and both monoclonal and field change models have been proposed. Low-grade dysplasia (18) and carcinoma in situ (12) associated with muscle-invasive urothelial carcinoma were microdissected and topographically analyzed (intraepithelial and invasive superficial and deep to muscularis mucosa) for methylation pattern of androgen receptor alleles, TP53, RB1, WT1, and NF1 microsatellite analysis to assess clonal identity; MLH1 and MSH2 sequencing/immunostaining. Appropriate controls were run. Carcinoma in situ (100%) and invasive urothelial carcinoma (100%) revealed monoclonal patterns, whereas low-grade dysplasia was preferentially polyclonal (80%). Carcinoma in situ showed aneuploid DNA content and more abnormal microsatellites than the corresponding invasive compartments, opposite to low-grade dysplasia. Absent MLH1 protein expression with no gene mutations were identified in carcinoma in situ and nodular-trabecular urothelial carcinoma with high microsatellite abnormalities. Somatic mismatch repair protein down-regulation and the accumulation of tumor suppressor gene microsatellite abnormalities contribute to a molecular evolution for monoclonal carcinoma in situ divergent from coexistent muscle-invasive urothelial carcinoma. Low-grade dysplasia is however unlikely connected with this molecular progression.

Differential kinetic features by tumour topography in cutaneous small-cell neuroendocrine (Merkel cell) carcinomas

BACKGROUND/OBJECTIVES

Merkel cell carcinomas (MCC) reveal epithelial and neuroendocrine differentiation, but its topographic cell kinetics remains unknown. This study analyses proliferation, apoptosis, and DNA ploidy by topography, features that can help planning therapeutic protocols. This study topographically analyses proliferation, apoptosis, and DNA ploidy.

METHODS

We selected 27 small-cell MCCs (expressing one epithelial and two neural markers, with consistent ultrastructural findings) to evaluate mitotic figure counting, Ki-67 index, apoptosis index based on the in situ end labelling of fragmented DNA (using Escherichia coli DNA polymerase I, Klenow fragment), DNA ploidy, and BCL2 and TP53 immuno-expression. At least 50 high-power fields were screened per topographic compartment (superficial or papillary dermis, and deep or reticular dermis), recording average and standard deviation for each variable. Variables were statistically compared in each tumour compartment using analysis of variance and Student's t-test (significant if P < 0.05).

RESULTS

MCCs revealed superficial aneuploid DNA content, and no topographic differences for proliferation markers. Apoptosis showed significantly lower values in the deep compartment (average, P = 0.0050, and standard deviation, P = 0.0074), correlating with increased BCL2 and TP53 immuno-expressions.

CONCLUSIONS

High homogeneously distributed proliferation and superficial aneuploid DNA content defines MCCs. Apoptosis follows proliferation in superficial compartments, being less variable and proliferation independent in deep compartments, where it is inversely correlated with BCL2/TP53 expression.

Microsatellite abnormalities and somatic down-regulation of mismatch repair characterize nodular-trabecular muscle-invasive urothelial carcinoma of the bladder

AIMS

To correlate histological infiltration patterns with genetic and mismatch repair (MMR) profiles in muscle-invasive bladder urothelial carcinomas (UroC).

METHODS AND RESULTS

Infiltration patterns were assessed in the deep compartment of muscle-invasive UroC (nodular-trabecular, 45 cases; infiltrative, 27 cases). Tumour compartment (superficial and deep to muscularis mucosa) analysis included: microsatellite pattern of TP53, RB1, WT1 and NF1 by polymerase chain reaction/denaturing gradient gel electrophoresis; mitotic, Ki67, in situ end labelling (ISEL) indices and DNA ploidy. MMR was assessed by MLH1 and MSH2 sequencing and immunohistochemistry in UroC with two or more abnormal microsatellite loci. Statistical differences were tested using anova and Fisher's exact tests. Infiltrative UroC showed lower Ki67 index 14.94 +/- 4.28, ISEL index 14.1 +/- 10.0 and shorter median survival (20 months) than nodular-trabecular UroC (Ki67 index 20.65 +/- 4.94, ISEL 20.2 +/- 22.7, 37-month survival, respectively). The genetic profile was significantly different for RB1 (P = 0.0003) and NF1 (P = 0.0023) only, being more frequently abnormal in nodular-trabecular UroC. A significant decrease in MLH1 or MSH2 protein expression with no gene mutations was identified in UroC with microsatellite abnormalities and a nodular-trabecular growth pattern.

CONCLUSIONS

Somatic down-regulation of MMR proteins in nodular-trabecular muscle-invasive UroC results in RB1/NF1 microsatellite abnormalities, correlating with higher cellular turnover and longer survival.

Precursor Lesions of the Adrenal Gland

OBJECTIVE

To review the existing literature for evidence that adrenocortical and adrenomedullary tumours develop through a multistep process of carcinogenesis.

RESULTS

In the adrenal cortex hyperplasia and adenomas are frequently observed tumours or tumour-like conditions. In contrast, adrenocortical carcinomas are rare. Based on well-validated histopathological scoring systems, benign and malignant adrenocortical tumours can be separated, although a small subset of tumours remains hard to classify. Although extensive follow-up studies might argue against multistep carcinogenesis, analysis of chromosomal imbalances and gene expression profiling studies in these tumours are inconclusive and could give support for both multistep pathogenesis or de novo genesis of carcinomas. A major limit to most of these studies is the small sample size and the lack of extensive clinical (follow-up) data. In the adrenal medulla, pheochromocytomas (PCC) are the most frequent tumours in adults, with an incidence of 8 per million. They can be divided into benign and malignant PCC, but the distinction can only be made when metastases are present. Arbitrarily, lesions of less than 1 cm in diameter are called hyperplastic, but it should be expected that the majority of these are early lesions and if left in situ would grow to classify as PCC. In contrast to cortical tumours, the frequent 1p and 3q loss as an early event in tumourigenesis of benign PCC is verified in multiple studies. However, studies in malignant PCC yield divergent results, due to the small numbers analysed.

CONCLUSION

Taken together, there appears to be a relationship between cortical and medullary hyperplasia on the one hand and cortical adenomas and PCC on the other. However, whether there is a transition from benign to malignant tumours, both cortical and medullary, remains to be determined.

Cytoarchitectural and kinetic features in the histological evaluation of follicular thyroid neoplasms

AIMS

The diagnosis of follicular thyroid carcinomas is mainly based on capsular and vascular invasion. The aim of this study was to determine the diagnostic relevance of nuclear features, inflammation and stromal changes.

METHODS AND RESULTS

Anisokaryosis, chromatin pattern, nucleolus, nuclear pleomorphism, nuclear/cytoplasmic ratio, necrosis, stromal changes and tumour interstitial lymphocytes (TIL) were analysed in adenomatous hyperplastic nodules (39), adenomas (43) and carcinomas (28 minimally invasive, 48 widely invasive and 27 anaplastic). Ki67 immunostaining, in situ end labelling (ISEL) for apoptosis and the Ki67/ISEL index were analysed by topographical compartments. Variables were compared by histological diagnosis using Fisher's exact test, analysis of variance and Student's t-tests and considered significant if P < 0.05. TIL were absent in 96% of neoplasms and 54% of adenomatous hyperplastic nodules. Conspicuous nucleoli, increased nuclear-cytoplasmic ratio and coexistent apoptosis-myxoid changes distinguished minimally invasive carcinomas from adenomas. The most specific variables of high-grade carcinoma were vasculonecrotic patterns, nuclear hyperchromatism and pleomorphism. A kinetic advantage predominated in the internal compartments of benign lesions and in the peripheral compartments of malignant lesions.

CONCLUSIONS

Follicular carcinomas show up-regulation of proliferation markers and the distinctive topographical kinetic profiles provide a basis for the distinction between benign and malignant and an explanation for the circumscription and encapsulation of benign lesions.

New concepts in adrenal vein sampling for aldosterone in the diagnosis of primary aldosteronism

Improved diagnostic techniques and adoption of a systematic and thorough diagnostic workup can lead to identification of the surgically correctable forms of primary aldosteronism (PA) far more frequently than expected. Adrenalectomy can provide long-term normalization of blood pressure and correction of PA in most patients with an aldosterone-producing adenoma. Forms needing surgical correction are generally held to be less common than forms requiring medical therapy; however, this can be a misconception arising from the lack of systematic use of adrenal vein sampling (AVS). Currently AVS still remains the "gold standard" for identifying unilateral causes of PA that are surgically curable. The criteria for selecting patients to undergo AVS, the technique for performing AVS, and the criteria for analyzing and interpreting its results are summarized here.

Whole genome expression profiling of glucose-dependent insulinotropic peptide (GIP)- and adrenocorticotropin-dependent adrenal hyperplasias reveals novel targets for the study of GIP-dependent Cushing's syndrome

CONTEXT

The mechanisms responsible for the ectopic adrenal expression of glucose-dependent insulinotropic peptide (GIP) receptor (GIPR) in GIP-dependent Cushing's syndrome (CS) are unknown. Chronic adrenal stimulation by ACTH in Cushing's disease or GIP in GIP-dependent ACTH-independent macronodular adrenal hyperplasia both lead to the induction of genes implicated in adrenal proliferation and steroidogenesis.

OBJECTIVE

The objective of the study was to identify genes differentially expressed specifically in GIP-dependent CS that could be implicated in the ectopic expression of GIPR.

METHODS

We used the Affymetrix U133 plus 2.0 microarray oligochips to compare the whole genome expression profile of adrenal tissues from five cases of GIP-dependent bilateral ACTH-independent macronodular adrenal hyperplasia with CS, one case of GIP-dependent unilateral adenoma with CS, five cases of ACTH-dependent hyperplasias, and a pool of adrenals from 62 normal individuals.

RESULTS

After data normalization and statistical filtering, 723 genes with differential expression were identified, including 461 genes or sequences with a known functional implication, classified in eight dominant functional classes. Specific findings include repression of perilipin, the overexpression of 13 G protein-coupled receptors, and the potential involvement of Rho-GTPases. We also isolated 94 probe sets potentially linked to the formation of GIP-dependent nodules adjacent to the diffuse hyperplasia. These included probe sets related to the linker histone H1 and repression of RXRa and CCND2. The expression profiles for eight genes were confirmed by real-time RT-PCR.

CONCLUSION

This study identified an extensive series of potentially novel target candidate genes that could be implicated in the molecular mechanisms of ectopic expression of the GIPR as well as in the multistep progression of GIP-dependent CS.

DNA and kinetic heterogeneity during the clonal evolution of adrenocortical proliferative lesions

Monoclonal adrenocortical lesions show inverse correlation between proliferation and apoptosis, with proliferation being the single most important criterion of malignancy in adrenal lesions. No study yet has evaluated the variability of proliferation regarding the clonal pattern and diagnosis in adrenocortical nodular hyperplasias (ACNHs), adrenocortical adenomas (ACAs), and adrenocortical carcinomas (ACCs). We studied 69 ACNHs, 64 ACAs, and 23 ACCs (World Health Organization criteria) from 156 females. Clonality HUMARA test (from microdissected DNA samples), DNA content and proliferation analysis (slide and flow cytometry), and mitotic figure (MF) counting/50 high-power fields (HPFs) were performed in the same areas. Heterogeneity was assessed by 5cER (percentage of nonoctaploid cells with DNA content exceeding 5c) and standard deviation of MF/HPF. Statistics included analysis of variance/Student t tests regarding the clonal patterns and diagnosis. Polyclonal patterns were observed in 48 of 62 informative ACNHs and 7 of 56 informative ACAs, and monoclonal in 14 of 62 ACNHs, 49 of 56 ACAs, and 21 of 21 ACCs, with all hyperdiploid lesions (14 ACCs and 13 ACAs) being monoclonal. The standard deviation of MF/HPF progressively increased in ACNH-ACA-ACC (0.048 +/- 0.076, 0.110 +/- 0.097, 0.506 +/- 0.291, respectively; P = .0023), but did not differentiate ACNH/ACA. Only tetraploid percentage (P = .0496) and 5cER (P = .0352) distinguished polyclonal (3.64 +/- 2.20 and 0.14 +/- 0.15) from monoclonal (7.25 +/- 7.52 and 1.00 +/- 1.74) benign lesions. Malignancy significantly correlated with a low diploid percentage and high tetraploid percentage. Cell kinetic heterogeneity is the hallmark of adrenocortical neoplasms: tetraploid/hypertetraploid cell accumulation characterizes monoclonal lesions (suggesting nondisjunctional mitoses), whereas heterogeneously distributed mitotic figures and decreased diploid percentage define ACCs.

Clinical and Subclinical ACTH-Independent Macronodular Adrenal Hyperplasia and Aberrant Hormone Receptors

ACTH-independent macronodular adrenal hyperplasia (AIMAH) is a very rare cause of endogenous Cushing's syndrome (CS). In this review, the clinical characteristics, the pathophysiology, and the management of AIMAH are described. AIMAH typically presents with overt CS, but subclinical oversecretion of cortisol has been increasingly described. The diagnosis is suspected by adrenal nodular enlargement on conventional imaging following the demonstration of ACTH-independent hypercortisolism. Final diagnosis is established by histological examination of the adrenal tissue. Bilateral adrenalectomy is the treatment of choice but unilateral adrenalectomy has been proposed in selected cases. In patients with subclinical CS, the decision to treat should be individualized. The pathophysiology of this condition has begun to be elucidated in recent years. Diverse aberrant membrane-bound receptors expressed in a non-mutated form in the adrenal gland have been found to be implicated in the regulation of steroidogenesis in AIMAH. When systematically screened, most patients with AIMAH and CS or subclinical CS exhibit an in vivo aberrant cortisol response to one or various ligands suggesting the presence of aberrant adrenal receptors. A protocol designed to screen patients for the presence of these aberrant receptors should be undertaken in all patients with AIMAH. The identification of these receptors provides the potential for novel pharmacological therapies by suppressing the endogenous ligands or blocking the receptor with specific antagonists.

Bilateral adrenal Cushing's syndrome: macronodular adrenal hyperplasia and primary pigmented nodular adrenocortical disease

Corticotropin (ACTH)-independent bilateral macronodular adrenal hyperplasia (AIMAH) and primary pigmented nodular adrenocortical disease (PPNAD) are responsible for approximately 10% of adrenal Cushing's syndrome. AIMAH also can be present as subclinical bilateral incidentalomas in sporadic or familial forms. Diverse aberrant hormone receptors have been found to be implicated in the regulation of steroidogenesis and pathophysiology of AIMAH. PPNAD can be found alone or in the context of Carney complex, a multiple endocrine neoplasia syndrome. Additionally, it can be secondary to mutations of type 1 alpha-regulatory subunit of cAMP-dependent protein kinase A (PRKARIA). Strategies for the investigation and treatment of AIMAH and PPNAD are discussed.

Irregular and frequent cortisol secretory episodes with preserved diurnal rhythmicity in primary adrenal Cushing's syndrome

To evaluate the pathophysiology of altered cortisol secretion in patients with primary adrenal hypercortisolism, cortisol secretion was investigated in 12 patients, seven with a unilateral adenoma and five with ACTH-independent macronodular adrenal hyperplasia compared with age- and gender-matched controls and with patients with pituitary-dependent hypercortisolism. Pulsatile secretion was increased 2-fold (P = 0.04), attributable to increased event frequency (P = 0.002). All patients showed a significant diurnal rhythm with a delay in phase shift of 3 h (P = 0.01). Approximate entropy ratio, a feedback-sensitive measure, was increased compared with controls (P = 0.00003) but similar to that of pituitary-dependent hypercortisolism (P = 0.77), denoting loss of autoregulation. Cortisol burst-mass tended to be smaller in patients with ACTH-independent macronodular adrenal hyperplasia than in unilateral adenoma (P = 0.06). In conclusion, increased cortisol secretion in patients with primary adrenal Cushing's syndrome is caused by amplified pulsatile secretion via event frequency modulation. We speculate that partial preservation of secretory regularity and diurnal rhythmicity point to incomplete autonomy of these tumors.

Handling and Pathology Reporting of Adrenal Gland Specimens

Proper treatment of resection specimens by the urologist and pathologist is critical in accurately reporting tumors and tumor-like nodules of the adrenal gland. Clinically inapparent adrenal masses are discovered, with increasing frequency, in the course of diagnostic testing or treatment for conditions that are not related to adrenal diseases. As a consequence an increasing number of relatively small tumors lacking the characteristic gross features of malignancy is detected. There is a need for identification of pathological findings that can improve the diagnostic accuracy and predict patient outcome. The aim of this paper is to review the handling and pathology reporting of adrenal gland specimens in the light of recent advances in this field of pathology.

Aberrant expression of hormone receptors in adrenal Cushing's syndrome

In recent years, a novel understanding of the pathophysiology of adrenal Cushing's syndrome has emerged. The ectopic or aberrant expression of G-protein-coupled hormone receptors in the adrenal cortex was found to play a central role in the regulation of cortisol secretion in ACTH-independent macronodular adrenal hyperplasia (AIMAH) and in some unilateral adrenal adenomas. Various aberrant receptors, functionally coupled to steroidogenesis, have been reported: GIP, vasopressin, beta-adrenergic, LH/hCG, and serotonin receptors have been best characterized, but angiotensin, leptin, glucagon, IL-1 and TSH receptors have also been described. The molecular mechanisms responsible for the aberrant expression of these receptors are currently unknown. One or many of these aberrant receptors are present in most cases of AIMAH and in some cases of adrenal adenomas with overt or sub-clinical secretion of cortisol. Clinical protocols to screen for such aberrant receptors have been developed and should be performed in all patients with AIMAH. The identification of such aberrant regulation of steroidogenesis in AIMAH provides the novel opportunity to treat some of these patients with pharmacological agents that either suppress the endogenous ligand or block the aberrant receptor, thus avoiding bilateral adrenalectomy.

The molecular pathogenesis of hereditary and sporadic adrenocortical and adrenomedullary tumors

Modern imaging modalities lead to frequent detection of adrenal masses, most of them incidental findings. Although the majority of adrenocortical and adrenomedullary tumors are benign, there are no reliable clinical and laboratory markers to distinguish most of them from malignant neoplasms. The molecular mechanisms underlying the pathogenesis of these tumors have recently begun to be unraveled. A fruitful avenue for the elucidation of tumorigenesis has been the study of adrenal tumors that are manifestations of hereditary or postzygotic genetic syndromes, because one knows the "first hit", i.e. the primary gene defect. In contrast, in sporadic adrenal tumors the first hit, possibly a somatic mutation of a tumor-related gene, is unknown, and therefore the sequence of genetic alterations is difficult to establish. In this article we review in addition to our own work the literature on molecular aspects of adrenocortical and adrenomedullary tumorigenesis.

Analysis of the progression of fibroepithelial tumours of the breast by PCR-based clonality assay

Fibroadenoma and phyllodes tumour of the breast are both fibroepithelial tumours. Although progression to epithelial malignancy has been described, the behaviour of most fibroadenomas is benign. Phyllodes tumours, on the other hand, can display locally destructive growth and can even metastasize. A relationship between the two tumours has been suggested in the literature. This study investigated the clonality of both the stroma and the epithelium of these fibroepithelial tumours and attempted to construct a model in which fibroadenoma can progress in both an epithelial and a stromal direction. Fibroadenomas (n=25) and phyllodes tumours (n=12) were selected for analysis. Tissue was microdissected and analysed for clonality using a polymerase chain reaction (PCR)-based assay targeted at an X-linked polymorphic marker, the human androgen receptor gene (HUMARA). Nineteen fibroadenomas and nine phyllodes tumours could be analysed. Normal-appearing epithelium, hyperplastic epithelium, and stroma removed from fibroadenomas were polyclonal. As expected, carcinoma in situ (CIS) removed from four fibroadenomas was monoclonal. Three areas of apparent stromal expansion within fibroadenoma were monoclonal, suggesting stromal progression. Mostly, the stroma of phyllodes tumours was monoclonal and the epithelium polyclonal. In two cases, however, the epithelium seemed to be monoclonal, whereas in three other cases the stromal component was polyclonal. These findings indicate that fibroadenoma can progress in an epithelial direction to CIS and in a stromal direction to phyllodes tumour.

Kinetic profiles by topographic compartments in muscle-invasive transitional cell carcinomas of the bladder: role of TP53 and NF1 genes

We evaluated 71 muscle-invasive transitional cell carcinomas (TCCs) of the bladder by tumor compartments. Kinetic parameters included mitotic figure counting, Ki-67 index, proliferation rate (DNA slide cytometry), and apoptotic index (in situ end labeling [ISEL] of fragmented DNA using digoxigenin-labeled deoxyuridine triphosphate and Escherichia coli DNA polymerase [Klenow fragment]). At least 50 high-power fields per compartment were screened from the same tumor areas; results are expressed as percentage of positive neoplastic cells. Mean and SD were compared by tumor compartment. DNA was extracted from microdissected samples (superficial and deep) and used for microsatellite analysis of TP53 and NF1 by polymerase chain reaction-denaturing gradient gel electrophoresis. Significantly higher marker scores were revealed in the superficial compartment than in the deep compartment. An ISEL index of less than 1% was revealed in 63% (45/71) of superficial compartments and 86% (61/71) of deep compartments. Isolated NF1 alterations were observed mainly in superficial compartments, whereas isolated TP53 abnormalities were present in deep compartments. Lower proliferation and down-regulation of apoptosis define kinetically the deep compartment of muscle-invasive TCC of the bladder and correlate with the topographic heterogeneity, NF1-defective in superficial compartments and TP53-defective in deep compartments.

Contribution of the microvessel network to the clonal and kinetic profiles of adrenal cortical proliferative lesions

Monoclonal adrenocortical lesions have been characterized by an inverse correlation between proliferation and apoptosis, and polyclonal lesions show a direct correlation. Their relationship with the vascular pattern remains unknown in adrenocortical nodular hyperplasias (ACNHs), adenomas (ACAs), and carcinomas (ACCs). We studied 20 ACNHs, 25 ACAs, and 10 ACCs (World Health Organization classification criteria) from 55 women. The analysis included X-chromosome inactivation assay (on microdissected samples), slide and flow cytometry, and in situ end labeling. Endothelial cells were stained with anti-CD31, and the blood vessel area and density were quantified by image analysis in the same areas. Appropriate tissue controls were run in every case. Regression analyses between kinetic and vascular features were performed in both polyclonal and monoclonal lesions. Polyclonal patterns were observed in 14 of 18 informative ACNHs and 3 of 22 informative ACAs, and monoclonal patterns were seen in 4 of 18 ACNHs, 19 of 22 ACAs, and 9 of 9 ACCs. A progressive increase in microvessel area was observed in the ACNH-ACA-ACC transition but was statistically significant between benign and malignant lesions only (191.36 +/- 168.32 v 958.07 +/- 1279.86 microm(2); P < .0001). In addition, case stratification by clonal pattern showed significant differences between polyclonal and monoclonal benign lesions; 6% of polyclonal and 57% of monoclonal lesions had microvessel area >186 microm(2) (P = .0000008). Monoclonal lesions showed parallel trends (but with opposite signs) for microvessel area and density in comparison with proliferation and apoptosis, whereas polyclonal lesions showed inverse trends. In conclusion, the kinetic advantage of monoclonal adrenal cortical lesions (increased proliferation, decreased apoptosis) is maintained by parallel increases in microvessel area and density.

Monoclonality of endocrine tumours: What does it mean?

It is believed and hoped that clonality assignment of tumours predicts long-term behaviour, narrows the search for the putative pathogenic event or events, identifies the extent of involvement of surrounding and distant tissues and assesses the completeness of surgical clearance. It should define optimal therapeutic strategies, such as gene therapy, and the most fruitful directions for research. Because the histological characteristics that are central to establishing prognosis in most neoplasms are of limited value in endocrine tumours, the benefits of interpretation of clonality are potentially even more valuable and far-reaching in these tissues. So, can clonality be accurately defined and, if it can, can the distinction between a polyclonal expansion of cells that are simply 'obeying orders' and the presumed progeny of a single anarchic mutant be usefully made? This review comes to the conclusion that the answer is 'probably not'.

Germline RET 634 mutation positive MEN 2A-related C-cell hyperplasias have genetic features consistent with intraepithelial neoplasia

C-cell hyperplasias are normally multifocal in multiple endocrine neoplasia type 2A. We compared clonality, microsatellite pattern of tumor suppressor genes, and cellular kinetics of C-cell hyperplasia foci in each thyroid lobe. We selected 11 females from multiple endocrine neoplasia type 2A kindred treated with thyroidectomy due to hypercalcitoninemia. C-cell hyperplasia foci were microdissected for DNA extraction to analyze the methylation pattern of androgen receptor alleles and microsatellite regions (TP53, RB1, WT1, and NF1). Consecutive sections were selected for MIB-1, pRB1, p53, Mdm-2, and p21WAF1 immunostaining, DNA content analysis, and in situ end labeling. Appropriate tissue controls were run. Only two patients had medullary thyroid carcinoma foci. Nine informative C-cell hyperplasia patients showed germline point mutation in RET, eight of them with the same androgen receptor allele preferentially methylated in both lobes. C-cell hyperplasia foci showed heterogeneous DNA deletions revealed by loss of heterozygosity of TP53 (12 of 20), RB1 (6 of 14), and WT1 (4 of 20) and hypodiploid G0/G1 cells (14 of 20), low cellular turnover (MIB-1 index 4.5%, in situ end labeling index 0.03%), and significantly high nuclear area to DNA index ratio. MEN 2A (germline point mutation in RET codon 634) C-cell hyperplasias are monoclonal and genetically heterogeneous and show down-regulated apoptosis, findings consistent with an intraepithelial neoplasia. Concordant X-chromosome inactivation and interstitial gene deletions suggest clone expansions of precursors occurring at a point in embryonic development before divergence of each thyroid lobe and may represent a paradigm for other germline mutations.

PCR techniques for clonality assays

Clonal overgrowths represent the hallmark of neoplastic proliferations, and their demonstration has been proved useful clinically for the diagnosis of malignant lymphomas based on the detection of specific and dominant immunoglobulin and/or T-cell receptor gene rearrangements. Nonrandom genetic alterations can also be used to test clonal expansions and the clonal evolution of neoplasms, especially analyzing hypervariable deoxyribonucleic acid (DNA) regions from patients heterozygous for a given marker. These tests rely basically on the demonstration of loss of heterozygosity (LOH) resulting from either hemizygosity (nonrandom interstitial DNA deletions) or homozygosity of mutant alleles observed in neoplasms. LOH analyses identify clonal expansions of a tumor cell population, and point to monoclonal proliferation when multiple and consistent LOH are demonstrated. Based on the methylation-related inactivation of one X chromosome in female subjects, X-linked markers (e.g., androgen receptor gene) will provide clonality information using LOH analyses after DNA digestion with methylation-sensitive restriction endonucleases. Therefore, both non-X-linked and X-linked analyses give complementary information, related and not related to the malignant transformation pathway respectively. Applied appropriately, these tools can establish the clonal evolution of tumor cell populations (tumor heterogeneity), identify early relapses, distinguish recurrent tumors from other metachronic neoplasms, and differentiate field transformation from metastatic tumor growths in synchronic and histologically identical neoplasms.

Critical analysis of histologic criteria for grading atypical (dysplastic) melanocytic nevi

Low concordance in grading atypical (dysplastic) melanocytic nevi (AMN) has been reported, and no systematic evaluation is available. We studied 123 AMN with architectural and cytologic atypia (40 associated with atypical-mole syndrome), classified according to standard criteria by 3 independent observers. Histologic variables included junctional and dermal symmetry, lateral extension, cohesion and migration of epidermal melanocytes, maturation, regression, nuclear features, nuclear grade, melanin, inflammatory infiltrate location, and fibroplasia. AMN (43 junctional and 80 compound) were graded mild (31), moderate (61), and severe (31). AMN-severe correlated with 3 or more nuclear abnormalities (especially pleomorphism, heterogeneous chromatin, and prominent nucleolus) and absence of regression, mixed junctional pattern, and suprabasilar melanocytes on top of lentiginous hyperplasia. AMN-severe diagnostic accuracy was 99.5% using these criteria, but only the absence of nuclear pleomorphism differentiated AMN-mild from AMN-moderate. No architectural features distinguishing AMN-mild from AMN-moderate were selected as significant by the discriminant analysis. AMN from atypical-mole syndrome revealed subtle architectural differences, but none were statistically significant in the discriminant analysis. Histologic criteria can reliably distinguish AMN-severe but fail to differentiate AMN-mild from AMN-moderate. AMN from atypical-mole syndrome cannot be diagnosed using pathologic criteria alone.

Clonal patterns in phaeochromocytomas and MEN-2A adrenal medullary hyperplasias: histological and kinetic correlates

The relationship among histological features, cell kinetics, and clonality has not been studied in adrenal medullary hyperplasias (AMHs) and phaeochromocytomas (PCCs). Thirty-four PCCs (23 sporadic and 11 MEN-2A (multiple endocrine neoplasia type 2A)-related tumours, the latter associated with AMH) from females were included in this study. Representative samples were histologically evaluated and microdissected to extract DNA and evaluate the methylation pattern of the androgen receptor alleles. At least two tissue samples (from the peripheral and internal zones in each tumour) were analysed with appropriate tissue controls run in every case. The same areas were selected for MIB-1 staining and in situ end labelling (ISEL). Malignant PCCs were defined by histologically confirmed distant metastases. All monoclonal AMH nodules from the same patient showed the same X-chromosome inactivated. Six sporadic PCCs revealed liver metastases (malignant PCC) and eight additional sporadic PCCs showed periadrenal infiltration (locally invasive PCC). All informative PCCs were monoclonal, except for five locally invasive PCCs and one benign PCC that revealed polyclonal patterns. Those cases also showed a fibroblastic stromal reaction with prominent blood vessels, focal smooth muscle differentiation, and significantly higher MIB-1 (126.8+/-29.9) and ISEL (50.9+/-12.8) indices. Concordant X-chromosome inactivation in nodules from a given patient suggests that MEN-2A AMH is a multifocal monoclonal condition. A subgroup of PCCs characterized by balanced methylation of androgen receptor alleles, high cellular turnover, and stromal proliferation also shows locally invasive features.