Case Report: Pheochromocytoma and Synchronous Neuroblastoma in a Family With Hereditary Pheochromocytoma Associated With a MAX Deleterious Variant

Early-Onset Sarcoma With Germline MAX Variant: Expanding the Spectrum in Hereditary Pheochromocytoma and Paraganglioma

Germline pathogenic variants in MYC-associated factor X (MAX) are a rare cause of hereditary pheochromocytoma and paraganglioma (PPGL) syndrome, typically presenting with pheochromocytomas (PCC). Although MAX-related PPGLs are generally characterized by an adrenergic phenotype and bilateral tumors in 67% of cases, the tumor spectrum associated with MAX pathogenic variants remains poorly understood. We present a case of a 28-year-old man with a germline MAX pathogenic variant (c.64-2A>G) who developed bilateral PCC and later, a liver sarcoma with a TP53 variant and PLEKHO2::BRAF gene fusion. The diagnosis of sarcoma in this young patient underscores a potential association between MAX pathogenic variants and an increased predisposition to sarcoma development. Our findings suggest that MAX-related PPGLs may be associated with other malignancies, including sarcoma, and support expanding surveillance guidelines to include whole-body imaging for early detection of extra-adrenal tumors. Given the rarity of MAX pathogenic variants, further studies are needed to elucidate the full spectrum of presentation and establish comprehensive evidence-based surveillance strategies.

Approach to the Paediatric Patient With Suspected Pheochromocytoma or Paraganglioma Versus Neuroblastoma

Catecholamine-producing tumors of childhood include neuroblastic tumors, phaeochromocytoma, and paraganglioma (PPGL). PPGL and neuroblastic tumors can arise in similar anatomical locations and clinical presentations can overlap, resulting in diagnostic challenges. Distinguishing between these tumor types is critical as management and long-term surveillance strategies differ depending on the diagnosis. Herein we describe 2 clinical cases and illustrate key considerations in the diagnostic workup of a neuroblastoma vs PPGL for patients presenting with adrenal, pelvic, and retroperitoneal masses in childhood.

Childhood Multiple Endocrine Neoplasia (MEN) Syndromes: Genetics, Clinical Heterogeneity and Modifying Genes

Multiple endocrine neoplasia (MEN) syndromes are part of a spectrum of clinically well-defined tumor syndromes ultimately characterized by histologically similar tumors arising in patients and families with mutations in one of the following four genes: MEN1, RET, CDKN1B, and MAX. The high level of genetic and phenotypic heterogeneity has been linked to phenocopies and modifying genes, as well as unknown mechanisms that might be investigated in the future based on preclinical and translational considerations. MEN1, also known as Wermer's syndrome (OMIM *131100), is an autosomal dominant syndrome codifying for the most frequent MEN syndrome showing high penetrance due to mutations in the MEN1 gene; nevertheless, clinical manifestations vary among patients in terms of tumor localization, age of onset, and clinical aggressiveness/severity, even within the same families. This has been linked to the effect of modifying genes, as described in the review. MEN 2-2b-4 and 5 also show remarkable clinical heterogeneity. The traditional view of genetically predisposing monogenic or multifactorial disorders is no longer valid, and mandates a change in scientific focus. Phenotypes are indeed rarely consistent across genetic backgrounds and environments. In the future, understanding factors and genetic variants that control cellular functions and the expression of disease genes should provide insights into fundamental disease processes, providing implications for counseling and therapeutic and prophylactic possibilities.

Genotype and clinical phenotype characteristics of MAX germline mutation-associated pheochromocytoma/paraganglioma syndrome

Objective

The aim of this study was to investigate the genotypic and clinical phenotypic characteristics of MAX germline mutation-associated pheochromocytoma (PCC) and paraganglioma (PGL).

Methods

We retrospectively analyzed the family investigation data and clinical genetic characteristics of six individuals from three independent families with PCC carrying MAX germline mutations from December 2005 to March 2024. A literature review was then conducted of the six carriers and another 103 carriers from the other 84 families with MAX germline mutations reported previously.

Results

There were 109 patients in 87 families with all five exons and 53 types of MAX germline mutations. p.R33* (c.97C>T; 21.1%), p.R75* (c.223C>T; 13.8%), and p.A67D (c.200C>A; 7.3%), which accounted for 42.2% of mutations detected, were the most common mutations. Moreover, 101 (92.7%) patients developed PCCs, including 59 bilateral PCCs and 42 unilateral PCCs, and 19 (18.8%) patients showed metastasis. The mean age at diagnosis was 32.8 ± 12.6 (13-80) years. The male-to-female ratio was 1.3:1. In 11 (10.9%) patients, the PCC was accompanied by chest or abdominal PGL, and one other patient had sole head and neck PGL. Nine (8.3%) patients also had functional pituitary adenomas, 11 (10.9%) developed other neuroendocrine tumors (NETs), and 7 (6.4%) presented with concomitant non-NET. Meanwhile, MAX-p.Q82Tfs*89 and p.E158A mutations are reported for the first time in this study.

Conclusion

MAX germline mutations may cause new types of multiple endocrine neoplasia. A comprehensive baseline assessment of neural crest cell-derived diseases is recommended for all individuals with MAX germline mutations. The risk of bilateral and metastatic PCCs should also be considered.

HIF and MYC signaling in adrenal neoplasms of the neural crest: implications for pediatrics

Pediatric neural crest-derived adrenal neoplasms include neuroblastoma and pheochromocytoma. Both entities are associated with a high degree of clinical heterogeneity, varying from spontaneous regression to malignant disease with poor outcome. Increased expression and stabilization of HIF2α appears to contribute to a more aggressive and undifferentiated phenotype in both adrenal neoplasms, whereas MYCN amplification is a valuable prognostic marker in neuroblastoma. The present review focuses on HIF- and MYC signaling in both neoplasms and discusses the interaction of associated pathways during neural crest and adrenal development as well as potential consequences on tumorigenesis. Emerging single-cell methods together with epigenetic and transcriptomic analyses provide further insights into the importance of a tight regulation of HIF and MYC signaling pathways during adrenal development and tumorigenesis. In this context, increased attention to HIF-MYC/MAX interactions may also provide new therapeutic options for these pediatric adrenal neoplasms.

Bilateral Pheochromocytoma with Germline MAX Variant without Family History

Recently, the genetic background of pheochromocytomas/paragangliomas (PPGLs) has been rapidly revealed. These tumors have been referred to as the “ten percent tumor”; however, the frequency of genetic variants of PPGLs has turned out to be more common than expected. PPGLs are potentially hereditary tumors and appear clinically sporadic. Here, we report a case of bilateral pheochromocytoma (PCC) with a variant in the MYC-associated factor X (MAX) gene (c.295 + 1G > A). A male patient was diagnosed with adrenal pheochromocytoma (PCC) and underwent a left adrenalectomy at the age of 40. A new tumor in the right adrenal gland was detected at the age of 43. Urinary metanephrine and normetanephrine concentrations gradually increased. The size of the right adrenal PCC continued to increase one year after detection. Genetic testing of the peripheral blood revealed the presence of a pathogenic variant in MAX. The natural history of adrenal PCCs with the MAX variant has not yet been clarified, because the number of reported cases is not sufficient. Thus, clinicians should consider a MAX variant when they find bilateral or multiple PCCs.

Biochemical Diagnosis of Catecholamine-Producing Tumors of Childhood: Neuroblastoma, Pheochromocytoma and Paraganglioma

Catecholamine-producing tumors of childhood include most notably neuroblastoma, but also pheochromocytoma and paraganglioma (PPGL). Diagnosis of the former depends largely on biopsy-dependent histopathology, but this is contraindicated in PPGL where diagnosis depends crucially on biochemical tests of catecholamine excess. Such tests retain some importance in neuroblastoma though continue to largely rely on measurements of homovanillic acid (HVA) and vanillylmandelic acid (VMA), which are no longer recommended for PPGL. For PPGL, urinary or plasma metanephrines are the recommended most accurate tests. Addition of methoxytyramine to the plasma panel is particularly useful to identify dopamine-producing tumors and combined with normetanephrine also shows superior diagnostic performance over HVA and VMA for neuroblastoma. While use of metanephrines and methoxytyramine for diagnosis of PPGL in adults is established, there are numerous pitfalls for use of these tests in children. The establishment of pediatric reference intervals is particularly difficult and complicated by dynamic changes in metabolites during childhood, especially in infants for both plasma and urinary measurements, and extending to adolescence for urinary measurements. Interpretation of test results is further complicated in children by difficulties in following recommended preanalytical precautions. Due to this, the slow growing nature of PPGL and neglected consideration of the tumors in childhood the true pediatric prevalence of PPGL is likely underappreciated. Earlier identification of disease, as facilitated by surveillance programs, may uncover the true prevalence and improve therapeutic outcomes of childhood PPGL. For neuroblastoma there remain considerable obstacles in moving from entrenched to more accurate tests of catecholamine excess.