BACKGROUND: 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.
METHODS: Retrospective observational nationwide study. Narrative review of literature and variant class reassessment.
METHODS: 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.
CONCLUSIONS: 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.

BACKGROUND: Hyperparathyroidism is caused by parathyroid tumors combined with gastroenteropancreatic tumors and pituitary tumors, which is common in patients with multiple endocrine neoplasia 1 syndrome (MEN-1). As its main pathogenic factor involves genetic mutations, it can cause a variety of different clinical symptoms. However, cases with negative genetic testing results and multiple nonfunctional malignant neuroendocrine tumors (NETs) with metastasis are relatively rare.
METHODS: A 33-year-old man was admitted to the hospital for hyperparathyroidism. Imaging examination revealed multiple nodules in the parathyroid gland, pancreas, thymus, and adrenal gland, and multiple metastases to the lung, liver, thoracolumbar, as well as mediastinal lymph nodes.
METHODS: After multidisciplinary consultation, this patient was diagnosed with MEN-1 syndrome with various original tumors and multiple systemic metastases.
METHODS: The patient underwent parathyroid tumor resection and metastasis biopsy.
RESULTS: The patient received denosumab and sorafenib treatment.
CONCLUSIONS: As an autosomal dominant hereditary disease, MEN-1 patients present with parathyroid hyperplasia, pancreatic and intestinal tumors, pituitary tumors, and so on, which are caused by genetic mutations. These patients would have hyperparathyroidism, hypoglycemia, gastric ulcer, and gastrointestinal diseases. However, some patients with MEN-1 syndrome cannot be diagnosed by genetic testing and simultaneously present with multiple nonfunctional NETs with systemic metastasis. This increases the difficulty of diagnosis and the subsequent treatment.

BACKGROUND: ACTH-independent macronodular hyperplasia (AIMAH) is an uncommon disorder characterized by massive enlargement of both adrenal glands and hypersecretion of cortisol. Concomitant AIMAH and multiple endocrine neoplasia type1 (MEN1) is rare to our knowledge.
METHODS: Herein, we describe a 32 year old woman with long history of prolactinoma and secondary ammonhrea presented with not-severe manifestation of hypoglycemia due to concomitant presence of insulinoma with AIMAH leading to 12 years delay of MEN1 diagnosis. Laboratory tests showed severe hypoglycemia associated with hyper insulinemia (non-fasting blood sugar = 43 mg/dl, insulin = 80.6 μIU /ml, C-peptide = 9.3 ng/ml) hyperparathyroidism (calcium = 10.3 mg/dl, phosphor = 3.1 mg/dl, PTH = 280 pg/ml) and chemical evidence of an ACTH-independent hypercortisolism (serum cortisol value of 3.5, after 1 mg dexamethasone suppression test serum ACTH value of 17 pg/ml, and high urinary cortisol level). Abdominal CT scan demonstrated two enhancing well-defined masses 27*20 mm and 37*30 mm in the tail and body of the pancreas, respectively, and a 36*15 mm mass in left adrenal gland (seven Hounsfield units). Dynamic pituitary MRI revealed a partial empty sella. The physical examination of the patient was unremarkable. Distal pancreatectomy and a left adrenalectomy were performed. After the surgery, we observed clinical and biochemical remission of hyper insulinemia and gradual decrease in urinary cortisol. The histological features of the removed left adrenal gland were consistent with AIMAH. Histological examination of the pancreatic lesions revealed well differentiated neuroendocrine tumors. Genetic abnormalities in the MEN1, heterozygote for pathogenic variant chr11; 645,773,330-64577333AGAC, c.249-252delGTCT, p. (11e85Serfs Ter33) in exon 2 were found. It was recommended the patient undergoes parathyroidectomy as soon as possible.
CONCLUSIONS: Given the history and presentation of our case, we recommend that the clinicians consider the possibility of autonomous cortisol production in MEN1 patients who do not show severe symptoms of hypoglycemia in the presence of insulinoma.

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.
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.
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.

BACKGROUND: PET of the somatostatine receptors (SSR) is a well-established functional imaging modality in the dia-gnosis of the neuroendocrine tumours (NET) of the gastro-entero-pancreatic origin (GEP). However, it can have a major impact also in other clinical entities.
OBJECTIVE: To present a literature review focusing on the effectivity of SSR PET in the dia-gnosis beyond GEP NET.
CONCLUSIONS: SSR PET provides an accurate dia-gnosis of pulmonary NET, pheochromocytoma and paraganglioma, it may have an important impact on their treatment and clinical management. It allows a detailed estimation of the extent of meningeoma, contributes to precise target volumes for radiotherapy delineation and is sensitive in its residuum or recurrence detection. It can be a valuable method in the syndromes of multiple endocrine neoplasia and in the localization of the source of the ectopic Cushing syndrome. It can be used in the medullary thyroid cancer. An important role of SSR PET lies in the planning and monitoring of the peptide-receptor radionuclide therapy embraced in the theranostic concept.

OBJECTIVE. The purpose of this article is to review the clinical manifestations, endocrine tumors types, and multimodality diagnostic tools available to physicians involved in the management of patients with multiple endocrine neoplasia (MEN) syndrome, in addition to discussing relevant imaging findings and appropriate imaging follow-up. CONCLUSION. Thorough knowledge of the spectrum of tumors associated with MEN gene mutations aids in the screening, diagnostic workup, and posttreatment monitoring of patients with MEN-related gene mutations.

The present study reported a rare case with thymic carcinoid as the first manifestation of multiple endocrine neoplasia type 1 (MEN1) syndrome, which presented with gene mutations of the MEN1 and glucokinase regulatory protein (GCKR). In this report, a 40-year-old male was diagnosed as MEN1 syndrome with thymic carcinoid, pancreatic cancer, hyperparathyroidism, and insulinoma with intrahepatic metastasis. Genetic testing showed the mutations of the MEN1 (c.378 G>A, p. Trp126*) in the patient, his children and two sisters, and GCKR (c.151C>T, p. Arg51*) gene in the patient and his children. The pathological examination showed that neuroendocrine tumor (NET) of the pancreas was characterized as 6 mitoses per 10 high-power fields (HPF), infiltration of adipose tissue, no intravascular tumor thrombus and nerve infiltration. In addition, NET of the liver was characterized as 4 mitoses per 10 HPF, no intravascular tumor thrombus and nerve infiltration. Immunohistochemical staining showed Ckpan (+), Syn (+), CgA (+), CD 56 (+), PGP 9.5 (+), and Ki67-positive cells (8-10%) in NET. Therefore, we suggested that genetic testing in family members of MEN1 patient, which may be helpful for early diagnosis.

Primary aldosteronism (PA) is a category of secondary hypertension induced by inhibition of the renin-angiotensin system due to increased aldosterone secretion. Aldosterone-producing adenoma (APA) is the most common hypotype of PA. Primary hyperparathyroidism (PHPT) refers to the symptoms of increased bone resorption and increased calcium reabsorption of kidney tubules caused by parathyroid secretion and excessive synthesis of parathyroid hormone. APA, complicated with PHPT has been extremely rare in clinical practice. In this study, the diagnosis and treatment of one case of APA complicated by PHPT was reported. Relevant literature review was performed.

OBJECTIVE: Dermal hyperneury is defined as the hypertrophy of small nerves in the dermis. It has been described in a variety of settings. We present a series of nine new cases with a distinctive clinical presentation and review the existing literature. The aim of the study was to summarise the clinical, histopathological and immunohistochemical findings in a case series of dermal hyperneury with unique clinical presentation.
RESULTS: Nine cases were identified from the referral practice of one of the authors. Clinical characteristics, including demographic details, were collated. The histopathological features and novel immunohistochemical findings were analysed. Four cases presented with multiple skin lesions. Clinical evaluation revealed no associated syndromic stigmata. The histology in all cases was that of dermal hyperneury. Immunohistochemistry for phosphatase and tensin homologue (PTEN) and RET was supportive of the lack of syndromic association.
CONCLUSIONS: The presentation of dermal hyperneury with multiple cutaneous lesions and no syndromic associations is distinctive, and no study with PTEN and RET immunohistochemistry has previously been reported. Comparisons with recent reports of multiple non-syndromic mucocutaneous neuromas are discussed.

The clinical phenotype of multiple endocrine neoplasia type 4 (MEN4) is undefined due to a limited number of published cases. Knowledge on disease manifestation in MEN4 is essential for developing prevention programs and treatment.
To expand current knowledge of the MEN4 phenotype including assessment of penetrance.
This is a case report and a brief review of previously published MEN4 cases.
We report a large Danish family with multiple cases of endocrine tumors that segregated with a pathogenic variant in the CDKN1B gene.
The medical history of the proband included primary hyperparathyroidism and Cushing disease. Genetic analysis identified a pathogenic variant in CDKN1B (c.121_122delTT, p.Leu41Asnfs*83). Among the family members, another 12 individuals were identified as carriers of the same variant, which segregated with development of endocrine tumors. Hypercalcemia due to primary hyperparathyroidism occurred in all 13 of the available carriers of the genetic variant, and 4 patients also had functioning or nonfunctioning pituitary adenomas, whereas 1 patient had a metastatic neuroendocrine tumor (carcinoid). Loss-of-heterozygosity was detected in two of five parathyroid adenomas, supporting that CDKN1B acts as a tumor suppressor gene. Thirty cases representing 16 different CDKN1B variants have previously been reported, and these cases presented primarily with primary hyperparathyroidism and functioning and nonfunctioning pituitary tumors.
Hypercalcemia due to primary hyperparathyroidism and pituitary tumors are common in MEN4. Gastrointestinal neuroendocrine tumors appear to be less prevalent in MEN4 than in MEN1.