CNC is genetically and clinically heterogeneous. Certain tumors are more frequent, with specific mutations providing some genotype-phenotype correlation for PRKAR1A mutations.

Malignant pheochromocytoma (PCC) and paraganglioma (PGL) are mostly caused by germline mutations of SDHB, encoding a subunit of succinate dehydrogenase. Using whole-exome sequencing, we recently identified a mutation in the FH gene encoding fumarate hydratase, in a PCC with an 'SDH-like' molecular phenotype. Here, we investigated the role of FH in PCC/PGL predisposition, by screening for germline FH mutations in a large international cohort of patients. We screened 598 patients with PCC/PGL without mutations in known PCC/PGL susceptibility genes. We searched for FH germline mutations and large deletions, by direct sequencing and multiplex ligation-dependent probe amplification methods. Global alterations in DNA methylation and protein succination were assessed by immunohistochemical staining for 5-hydroxymethylcytosine (5-hmC) and S-(2-succinyl) cysteine (2SC), respectively. We identified five pathogenic germline FH mutations (four missense and one splice mutation) in five patients. Somatic inactivation of the second allele, resulting in a loss of fumarate hydratase activity, was demonstrated in tumors with FH mutations. Low tumor levels of 5-hmC, resembling those in SDHB-deficient tumors, and positive 2SC staining were detected in tumors with FH mutations. Clinically, metastatic phenotype (P = 0.007) and multiple tumors (P = 0.02) were significantly more frequent in patients with FH mutations than those without such mutations. This study reveals a new role for FH in susceptibility to malignant and/or multiple PCC/PGL. Remarkably, FH-deficient PCC/PGLs display the same pattern of epigenetic deregulation as SDHB-mutated malignant PCC/PGL. Therefore, we propose that mutation screening for FH should be included in PCC/PGL genetic testing, at least for tumors with malignant behavior.

AIMAH is a clinically and genetically heterogeneous disorder that can be associated with various genetic defects and aberrant hormone receptors. It is frequently associated with atypical CS and increased 17OHS; UFCs and other measures of adrenocortical activity can be misleadingly normal.

Inherited autosomal dominant mutations in the ARMC5 gene are a frequent cause of PMAH. Biallelic inactivation of ARMC5 is consistent with its role as a potential tumor suppressor gene.

Stimulation with ACTH is useful to improve selectivity of AVS but can frequently modify interpretation of lateralization. Basal ratios are as important as post-ACTH ratios to set an indication of adrenalectomy. AOPP/AP is superior to (A/C)OPP/(A/C)P to assess contralateral suppression. Infrequent CL suppression reveals frequent occurrence of contralateral hyperplasia in lateralized cases and helps predict postoperative outcomes.

Activating mutations of exon 3 of the beta-catenin gene are frequent in adrenocortical adenomas, and further characterization of the Wnt/beta-catenin signalling pathway should lead to a better understanding of adrenal tumourigenesis.

Summary The aberrant adrenal expression and function of one or several G‐protein coupled receptors can lead to cell proliferation and abnormal regulation of steroidogenesis in unilateral adenomas, carcinomas or in ACTH‐independent macronodular adrenal hyperplasia (AIMAH). Excess cortisol secretion leading to either sub‐clinical or overt Cushing’s syndrome is the most prevalent phenotype reported to date. In a few patients, aberrant regulation of androgen excess has been reported. More recently, initial studies suggest that similar mechanisms are involved in the renin‐independent regulation of aldosterone secretion in primary aldosteronism. In recent years, cases of familial AIMAH have been identified, and specific aberrant hormone receptors are functional in the adrenal of affected members. The identification of aberrant receptors can offer specific pharmacological approach to prevent disease progression and control abnormal steroidogenesis; alternatively, unilateral or bilateral adrenalectomy remains the treatment of choice.

Cortisol secretion in adrenal Cushing's syndrome can be regulated by the aberrant adrenal expression of receptors for gastric inhibitory polypeptide, vasopressin, catecholamines, LH/human CG (LH/hCG), or serotonin. Four patients with incidentally discovered bilateral macronodular adrenal hyperplasia without clinical Cushing's syndrome were evaluated for the possible presence of aberrant adrenocortical hormone receptors. Urinary free cortisol levels were within normal limits, but plasma cortisol levels were slightly elevated at nighttime and suppressed incompletely after dexamethasone administration. Plasma ACTH was partially suppressed basally but increased after administration of ovine CRH. A 51-yr-old woman had ACTH-independent increases of plasma cortisol after 10 IU AVP im (292%), 100 microg GnRH iv (184%), or 10 mg cisapride orally (310%); cortisol also increased after administration of NaCl (3%), hCG, human LH, and metoclopramide. In a 61-yr-old man, cortisol was increased by AVP (349%), GnRH (155%), hCG (252%), and metoclopramide (191%). Another 53-yr-old male increased plasma cortisol after AVP (171%) and cisapride (142%). Cortisol secretion was also stimulated by vasopressin in a 54-yr-old female. This study demonstrates that subclinical secretion of cortisol can be regulated via the aberrant function of at least V1-vasopressin, LH/hCG, or 5-HT4 receptors in incidentally identified bilateral macronodular adrenal hyperplasia.