Hereditary paraganglioma-pheochromocytoma (PGL/PCC) syndromes are characterized by paragangliomas and pheochromocytomas and have been associated with germline heterozygous mutations in MAX, SDHA, SDHAF2, SDHB, SDHC, SDHD, or TMEM127.
The objective of the present study was to present our experience with contrast-enhanced computed tomography (CT) and 18F-fluorodihydroxyphenylalanine (18F-FDOPA) positron emission tomography (PET)/CT in six consecutive patients (four at the initial diagnosis and two at the follow-up evaluation) with rare, but clinically important, MAX-related PHEOs.
Case 2 is a 54-year-old woman with a PCC/PGL syndrome caused by a mutation in MAX gene (c.171+1G>A), operated on for bilateral adrenal PCC and presenting with a large unresectable abdominal PGL.
Literature review revealed evidence of an association, in addition to VHL disease, between germline mutations in SDHB, SDHC, SDHD, TMEM127, and MAX genes and RAPTAS [defined here as the co-occurrence of tumors from both classes (PC/PGL/HNPGL and renal tumors) in the same individual or in first-degree relatives].
Uniparental disomy of chromosome 14q, previously demonstrated as a hallmark for MAX-related PCC, was shown in the index patient's PCC by single-nucleotide polymorphism array.
The presence of germline mutations affecting the MYC-associated protein X (MAX) gene has recently been identified as one of the now 11 major genetic predisposition factors for the development of hereditary pheochromocytoma and/or paraganglioma.
About 60% of Pheochromocytoma (PCC) and Paraganglioma (PGL) patients have either germline or somatic mutations in one of the 12 proposed disease causing genes; SDHA, SDHB, SDHC, SDHD, SDHAF2, VHL, EPAS1, RET, NF1, TMEM127, MAX and H-RAS.
Pheochromocytomas and paragangliomas (PPGLs) are catecholamine-producing chromaffin cell tumors with diverse phenotypic features reflecting mutations in numerous genes, including MYC-associated factor X (MAX).
Indeed 14q deletion is a recurrent somatic rearrangement in NB and MAX somatic and germline loss of function mutation have recently been described in pheochromocytoma and paraganglioma.
Analysis of the MAX gene should be performed in selected patients, especially those with bilateral adrenal phaeochromocytoma in whom mutations of the classical genes are absent.
Upregulation of miR-210 in VHL- and SDHB-related PCCs/PGLs was verified, while miR-137 and miR-382 were confirmed as generally upregulated in PCCs/PGLs (except in MAX-related tumors).
In this study, we elucidate some of the molecular mechanisms behind sporadic pheochromocytoma by performing a comprehensive analysis of copy number alterations, gene expression, promoter methylation and somatic mutations in the genes RET, VHL, NF1, SDHA, SDHB, SDHC, SDHD, SDHAF2, KIF1Bβ, TMEM127 and MAX, which have been associated with hereditary pheochromocytoma or paraganglioma.
Genetic analysis for PHEO/paraganglioma genes (SDH A-D, SDHAF2, RET, VHL, TMEM127, and MAX), and pituitary-related genes (AIP, MEN1, and p27) were negative.
The involvement of the MYC-MAX-MXD1 network in the development and progression of neural crest cell tumors is further supported by the lack of functional MAX in rat PCC (PC12) cells and by the amplification of MYCN in neuroblastoma and suggests that loss of MAX function is correlated with metastatic potential.