Co-occurrence of multiple endocrine neoplasia type 4 and spinal neurofibromatosis: a case report

Beyond MEN1, When to Think About MEN4? Retrospective Study on 5600 Patients in the French Population and Literature Review

CONTEXT

Germline CDKN1B variants predispose patients to multiple endocrine neoplasia type 4 (MEN4), a rare MEN1-like syndrome, with <100 reported cases since its discovery in 2006. Although CDKN1B mutations are frequently suggested to explain cases of genetically negative MEN1, the prevalence and phenotype of MEN4 patients is poorly known, and genetic counseling is unclear.

OBJECTIVE

To evaluate the prevalence of MEN4 in MEN1-suspected patients and characterize the phenotype of MEN4 patients.

DESIGN

Retrospective observational nationwide study. Narrative review of literature and variant class reassessment.

PATIENTS

We included all adult patients with class 3/4/5 CDKN1B variants identified by the laboratories from the French Oncogenetic Network on Neuroendocrine Tumors network between 2015 and 2022 through germline genetic testing for MEN1 suspicion. After class reassessment, we compared the phenotype of symptomatic patients with class 4/5 CDKN1B variants (ie, with genetically confirmed MEN4 diagnosis) in our series and in literature with 66 matched MEN1 patients from the UMD-MEN1 database.

RESULTS

From 5600 MEN1-suspected patients analyzed, 4 with class 4/5 CDKN1B variant were found (0.07%). They presented with multiple duodenal NET, primary hyperparathyroidism (PHPT) and adrenal nodule, isolated PHPT, PHPT, and pancreatic neuroendocrine tumor. We listed 29 patients with CDKN1B class 4/5 variants from the literature. Compared with matched MEN1 patients, MEN4 patients presented lower NET incidence and older age at PHPT diagnosis.

CONCLUSION

The prevalence of MEN4 is low. PHPT and pituitary adenoma represent the main associated lesions, NETs are rare. Our results suggest a milder and later phenotype than in MEN1. Our observations will help to improve genetic counseling and management of MEN4 families.

Familial states of primary hyperparathyroidism: an update

BACKGROUND

Familial primary hyperparathyroidism (PHPT) includes syndromic and non-syndromic disorders. The former are characterized by the occurrence of PHPT in association with extra-parathyroid manifestations and includes multiple endocrine neoplasia (MEN) types 1, 2, and 4 syndromes, and hyperparathyroidism-jaw tumor (HPT-JT). The latter consists of familial hypocalciuric hypercalcemia (FHH) types 1, 2 and 3, neonatal severe primary hyperparathyroidism (NSHPT), and familial isolated primary hyperparathyroidism (FIHP). The familial forms of PHPT show different levels of PHPT penetrance, developing earlier and with multiglandular involvement compared to sporadic counterpart. All these diseases exhibit Mendelian inheritance patterns, and for most of them, the genes responsible have been identified. DNA testing for predisposing mutations is helpful in index cases or in individuals with a high suspicion of the disease. Early recognition of hereditary disorders of PHPT is of great importance for the best clinical and surgical approach. Genetic testing is useful in routine clinical practice because it will also involve appropriate screening for extra-parathyroidal manifestations related to the syndrome as well as the identification of asymptomatic carriers of the mutation.

PURPOSE

The aim of the review is to discuss the current knowledge on the clinical and genetic profile of these disorders along with the importance of genetic testing in clinical practice.

Paraneoplastic Syndromes in Neuroendocrine Prostate Cancer: A Systematic Review

Neuroendocrine prostate cancer (NEPC) is a rare subtype of prostate cancer (PCa) that usually results in poor clinical outcomes and may be accompanied by paraneoplastic syndromes (PNS). NEPC is becoming more frequent. It can initially manifest as PNS, complicating diagnosis. Therefore, we reviewed the literature on the different PNS associated with NEPC. We systematically reviewed English-language articles from January 2017 to September 2023, identifying 17 studies meeting PRISMA guidelines for NEPC and associated PNS. A total of 17 articles were included in the review. Among these, Cushing's Syndrome (CS) due to ectopic Adrenocorticotropic hormone (ACTH) secretion was the most commonly reported PNS. Other PNS included syndrome of inappropriate Anti-Diuretic Hormone secretion (SIADH), Anti-Hu-mediated chronic intestinal pseudo-obstruction (CIPO), limbic encephalitis, Evans Syndrome, hypercalcemia, dermatomyositis, and polycythemia. Many patients had a history of prostate adenocarcinoma treated with androgen deprivation therapy (ADT) before neuroendocrine features developed. The mean age was 65.5 years, with a maximum survival of 9 months post-diagnosis. NEPC is becoming an increasingly more common subtype of PCa that can result in various PNS. This makes the diagnosis and treatment of NEPC challenging. Further research is crucial to understanding these syndromes and developing standardized, targeted treatments to improve patient survival.

Novel germline variants of CDKN1B and CDKN2C identified during screening for familial primary hyperparathyroidism

PURPOSE

CDKN1B mutations were established as a cause of multiple endocrine neoplasia 4 (MEN4) syndrome in patients with MEN1 phenotype without a mutation in the MEN1 gene. In addition, variants in other cyclin-dependent kinase inhibitors (CDKIs) were found in some MEN1-like cases without the MEN1 mutation. We aimed to describe novel germline mutations of these genes in patients with primary hyperparathyroidism (PHPT).

METHODS

During genetic screening for familial hyperparathyroidism, three novel CDKIs germline mutations in three unrelated cases between January 2019 and November 2021 were identified. In this report, we describe clinical features, DNA sequence analysis, and familial segregation studies based on these patients and their relatives. Genome-wide DNA study of loss of heterozygosity (LOH), copy number variation (CNV), and p27/kip immunohistochemistry was performed on tumour samples.

RESULTS

DNA screening was performed for atypical parathyroid adenomas in cases 1 and 2 and for cystic parathyroid adenoma and young age at diagnosis of PHPT in case 3. Genetic analysis identified likely pathogenic variants of CDKN1B in cases 1 and 2 and a variant of the uncertain significance of CDKN2C, with uniparental disomy in the tumour sample, in case 3. Neoplasm screening of probands showed other non-endocrine tumours in case 1 (colon adenoma with dysplasia and atypical lipomas) and case 2 (aberrant T-cell population) and a non-functional pituitary adenoma in case 3.

CONCLUSION

Germline mutations in CDKIs should be included in gene panels for genetic testing of primary hyperparathyroidism. New germline variants here described can be added to the current knowledge.

Germline CDKN1B variant type and site are associated with phenotype in MEN4

Multiple endocrine neoplasia 4 (MEN4) is a rare multiglandular endocrine neoplasia syndrome clinically hallmarked by primary hyperparathyroidism (PHPT), pituitary adenoma (PitAd), and neuroendocrine tumors (NET), clinically overlapping MEN1. The underlying mutated gene - CDKN1B, encodes for the cell-cycle regulator p27. Possible genotype-phenotype correlations in MEN4 have not been thoroughly assessed. Prompted by the findings in three Israeli MEN4 kindreds, we performed a literature review on published and unpublished data from previously reported MEN4/CDKN1B cases. Univariate analysis analyzed time-dependent risks for developing PHPT, PitAd, or NET by variant type and position along the gene. Overall, 74 MEN4 cases were analyzed. PHPT risk was 53.4% by age 60 years (mean age at diagnosis age 50.6 ± 13.9 years), risk for PitAd was 23.2% and risk for NET was 16.2% (34.4 ± 21.4 and 52.9 ± 13.9 years, respectively). The frameshift variant p.Q107fs was the most common variant identified (4/41 (9.7%) kindreds). Patients with indels had higher risk for PHPT vs point mutations (log-rank, P = 0.029). Variants in codons 94-96 were associated with higher risk for PHPT (P < 0.001) and PitAd (P = 0.031). To conclude, MEN4 is clinically distinct from MEN1, with lower risk and older age for PHPT diagnosis. We report recurrent CDKN1B frameshift variants and possible genotype-phenotype correlations.

MEN4, the MEN1 Mimicker: A Case Series of three Phenotypically Heterogenous Patients With Unique CDKN1B Mutations

CONTEXT

Germline CDKN1B pathogenic variants result in multiple endocrine neoplasia type 4 (MEN4), an autosomal dominant hereditary tumor syndrome variably associated with primary hyperparathyroidism, pituitary adenoma, and duodenopancreatic neuroendocrine tumors.

OBJECTIVE

To report the phenotype of 3 unrelated cases each with a unique germline CDKN1B variant (of which 2 are novel) and compare these cases with those described in the current literature.

DESIGN/METHODS

Three case studies, including clinical presentation, germline, and tumor genetic analysis and family history.

SETTING

Two tertiary University Hospitals in Sydney, New South Wales, and 1 tertiary University Hospital in Canberra, Australian Capital Territory, Australia.

OUTCOME

Phenotype of the 3 cases and their kindred; molecular analysis and tumor p27kip1 immunohistochemistry.

RESULTS

Family A: The proband developed multiglandular primary hyperparathyroidism, a microprolactinoma and a multifocal nonfunctioning duodenopancreatic neuroendocrine tumor. Family B: The proband was diagnosed with primary hyperparathyroidism from a single parathyroid adenoma. Family C: The proband was diagnosed with a nonfunctioning pituitary microadenoma and ectopic Cushing's syndrome from an atypical thymic carcinoid tumor. Germline sequencing in each patient identified a unique variant in CDKN1B, 2 of which are novel (c.179G > A, p.Trp60*; c.475G > A, p.Asp159Asn) and 1 previously reported (c.374_375delCT, p.Ser125*).

CONCLUSIONS

Germline CDKN1B pathogenic variants cause the syndrome MEN4. The phenotype resulting from the 3 pathogenic variants described in this series highlights the heterogenous nature of this syndrome, ranging from isolated primary hyperparathyroidism to the full spectrum of endocrine manifestations. We report the first described cases of a prolactinoma and an atypical thymic carcinoid tumor in MEN4.

Pancreatic Neuroendocrine Neoplasms: Updates on Genomic Changes in Inherited Tumour Syndromes and Sporadic Tumours Based on WHO Classification

Pancreatic neuroendocrine neoplasms (PanNENs) are the neuroendocrine neoplasms with greatest rate of increase in incidence. Approximately 10% of PanNENs arise as inherited tumour syndromes which include multiple endocrine neoplasia type 1, multiple endocrine neoplasia type 4, von Hippel-Lindau syndrome, neurofibromatosis type1, tuberous sclerosis complex 1/2, Cowden syndrome, and Glucagon cell hyperplasia and neoplasia as well as familial insulinomatosis. In sporadic PanNENs, driver mutations in MEN1, DAXX/ATRX and mTOR pathway genes are associated with development and progression in pancreatic neuroendocrine tumours. The other changes are in VEGF pathway, Notch pathway, germline mutations in MUTYH, CHEK2, BRCA2, PHLDA3 as well as other genetic alterations. On the other hand, pancreatic neuroendocrine carcinomas share similar genetic alterations with ductal adenocarcinomas, e.g., TP53, RB1 or KRAS. In addition, microRNA and changes in immune microenvironment were noted in PanNENs. Updates on these genetic knowledges contribute to the development of management strategies for patients with PanNENs.

Case Report: New CDKN1B Mutation in Multiple Endocrine Neoplasia Type 4 and Brief Literature Review on Clinical Management

BACKGROUND

The fourth type of multiple endocrine neoplasia (MEN) is known as a rare variant of MEN presenting a MEN1-like phenotype and originating from a germline mutation in CDKN1B. However, due to the small number of cases documented in the literature, the peculiar clinical features of MEN4 are still largely unknown, and clear indications about the clinical management of these patients are currently lacking. In order to widen our knowledge on MEN4 and to better typify the clinical features of this syndrome, we present two more cases of subjects with MEN4, and through a review of the current literature, we provide some possible indications on these patients' management.

CASE PRESENTATION

The first report is about a man who was diagnosed with a metastatic ileal G2-NET at the age of 34. Genetic analysis revealed the mutation p.I119T (c.356T>C) of exon 1 of CDKN1B, a mutation already reported in the literature in association with early-onset pituitary adenomas. The second report is about a 76-year-old woman with a multifocal pancreatic G1-NET. Genetic analysis identified the CDKN1B mutation c.482C>G (p.S161C), described here for the first time in association with MEN4 and currently classified as a variant of uncertain significance. Both patients underwent biochemical and imaging screening for MEN1-related diseases without any pathological findings.

CONCLUSIONS

According to the cases reported in the literature, hyperparathyroidism is the most common clinical feature of MEN4, followed by pituitary adenoma and neuroendocrine tumors. However, MEN4 appears to be a variant of MEN with milder clinical features and later onset. Therefore, these patients might need a different and personalized approach in clinical management and a peculiar screening and follow-up strategy.