Is there still a place for adrenal venous sampling in the diagnostic localization of pheochromocytoma?

Next-generation panel sequencing identifies NF1 germline mutations in three patients with pheochromocytoma but no clinical diagnosis of neurofibromatosis type 1

OBJECTIVE

Our objective was to improve molecular diagnostics in patients with hereditary pheochromocytoma and paraganglioma (PPGL) by using next-generation sequencing (NGS) multi-gene panel analysis. Derived from this study, we here present three cases that were diagnosed with NF1 germline mutations but did not have a prior clinical diagnosis of neurofibromatosis type 1 (NF1).

DESIGN

We performed genetic analysis of known tumor predisposition genes, including NF1, using a multi-gene NGS enrichment-based panel applied to a total of 1029 PPGL patients. We did not exclude genes known to cause clinically defined syndromes such as NF1 based on missing phenotypic expression as is commonly practiced.

METHODS

Genetic analysis was performed using NGS (TruSight Cancer Panel/customized panel by Illumina) for analyzing patients' blood and tumor samples. Validation was carried out by Sanger sequencing.

RESULTS

Within our cohort, three patients, who were identified to carry pathogenic NF1 germline mutations, attracted attention, since none of the patients had a clinical suspicion of NF1 and one of them was initially suspected to have MEN2A syndrome due to co-occurrence of a medullary thyroid carcinoma. In these cases, one splice site, one stop and one frameshift mutation in NF1 were identified.

CONCLUSIONS

Since phenotypical presentation of NF1 is highly variable, we suggest analysis of the NF1 gene also in PPGL patients who do not meet diagnostic NF1 criteria. Co-occurrence of medullary thyroid carcinoma and PPGL was found to be a clinical decoy in NF1 diagnostics. These observations underline the value of multi-gene panel NGS for PPGL patients.

Adrenal venous catecholamine concentrations in patients with adrenal masses other than pheochromocytoma

The aim of this study was to retrospectively examine adrenal venous catecholamine concentrations and related indices in non-pheochromocytoma patients and to estimate from the obtained results whether measurements of adrenal venous catecholamine concentrations by adrenal venous sampling (AVS) are useful for localizing adrenal pheochromocytoma. The study population comprised 15 patients in whom AVS was performed for evaluation of adrenal non-pheochromocytoma masses (primary aldosteronism, n = 8; Cushing syndrome, n = 5; non-hyperfunctioning tumor, n = 2) without hormonal intervention and was successful in bilaterally judging adrenal vein to infra-renal inferior vena cava cortisol ratios as >3.0. Wide ranges of catecholamine concentrations were seen for both right (epinephrine, 35-175,821 pg/ml; norepinephrine, 115-32,102 pg/ml; dopamine, 9-232 pg/ml) and left (epinephrine, 16-27,251 pg/ml; norepinephrine, 155-9,267 pg/ml; dopamine, 5-234 pg/ml) adrenal veins. High- to low-side adrenal vein concentration ratios also showed wide ranges of up to 779 for epinephrine, 22.5 for norepinephrine, and 7.8 for dopamine. Adrenal venous catecholamine concentrations obtained by AVS and simple comparisons between bilateral adrenal veins might not be useful to localize adrenal pheochromocytoma, as wide variations in concentrations and high- to low-side adrenal vein concentration ratios were noted in patients with adrenal non-pheochromocytoma.

Mini-review: pheochromocytomas causing the ectopic ACTH syndrome

Cushing's syndrome (CS) is a condition associated with high cortisol levels and affects around 0.7-2.4 cases per million population per year [1-3]. Approximately 80 % of cases of CS are secondary to excess adrenocorticotrophin (ACTH) secretion, while in around 20 % the primary abnormality lies in the adrenal, most often an adrenal adenoma or carcinoma. Of the ACTH-dependent causes, some 80-90 % are due to a pituitary adenoma-Cushing's disease-but in a significant proportion the cause is ectopic secretion from a non-pituitary source, the ectopic ACTH syndrome (EAS) [4]. The commonest source of ACTH secretion in these patients is a bronchial carcinoid. However, many other tumors are capable of secreting ACTH, and in most series a small but significant number are secondary to an ACTH-secreting pheochromocytoma. Amalgamating the data from 6 large series of patients with ectopic ACTH, pheochromocytoma was the source of ACTH secretion in 19 out of 363 patients (5.2 %) [5-11]. In this mini-review, we present a patient presenting to our department with a pheochromocytoma as well as Cushing's syndrome due to ectopic ACTH secretion by the pheochromocytoma, and we discuss published cases in the world literature to assess its significance. We emphasize the problems in the simultaneous management of these two serious endocrine conditions.

Pheochromocytoma - update on disease management

Pheochromocytomas are rare endocrine tumors that can present insidiously and remain undiagnosed until death or onset of clear manifestations of catecholamine excess. They are often referred to as one of the 'great mimics' in medicine. These tumors can no longer be regarded as a uniform disease entity, but rather as a highly heterogeneous group of chromaffin cell neoplasms with different ages of onset, secretory profiles, locations, and potential for malignancy according to underlying genetic mutations. These aspects all have to be considered when the tumor is encountered, thereby enabling optimal management for the patient. Referral to a center of specialized expertise for the disease should be considered wherever possible. This is not only important for surgical management of patients, but also for post-surgical follow up and screening of disease in patients with a hereditary predisposition to the tumor. While preoperative management has changed little over the last 20 years, surgical procedures have evolved so that laparoscopic resection is the standard of care and partial adrenalectomy should be considered in all patients with a hereditary condition. Follow-up testing is essential and should be recommended and ensured on a yearly basis. Managing such patients must now also take into account possible underlying mutations and the appropriate selection of genes for testing according to disease presentation. Patients and family members with identified mutations then require an individualized approach to management. This includes consideration of distinct patterns of biochemical test results during screening and the appropriate choice of imaging studies for tumor localization according to the mutation and associated differences in predisposition to adrenal, extra-adrenal and metastatic disease.