Multiple endocrine neoplasia syndrome type 1 (MEN-1) is a rare, autosomal dominant disorder resulting from inactivating mutations in the MEN1 gene. It demonstrates high penetrance, with the "classic triad" of manifestations comprising primary hyperparathyroidism (PHPT), gastrointestinal neuroendocrine neoplasms (NEN), and pituitary adenomas. Diagnosis relies on clinical, familial, and genetic criteria. However, significant phenotypic variability and the lack of a clear genotype-phenotype correlation complicate early diagnosis.

Thyroid nodules in children are relatively rare; the risk of malignancy is considerably higher compared to adults. The optimal extent of surgery, the indications for radioactive iodine therapy (RAI), and the role of molecular genetic testing in children with thyroid carcinoma remain a matter of debate.

Von Hippel-Lindau syndrome (FHL) is a rare autosomal dominant disease that leads to the formation of multiple organ tumor syndrome. The pathology is primarily caused by the inactivation of the VHL gene, which is located on chromosome 3 (3p25/26) and encodes ubiquitin ligase, which destroys hypoxia-induced factor-1α (HIF-1α). The genetic defect leads to the accumulation of HIF-1a protein, activating key carcinogenic pathways, and activated cytokines cause abnormal proliferation of tumor cells and oncogenesis. To date, more than 500 mutations have been registered in VHL. FHL syndrome is characterized by various tumors, including hemangioblastomas of the retina and central nervous system, pheochromocytomas, clear cell renal cell carcinoma, cystic adenoma and others. In the presented clinical description, pheochromocytoma was initially diagnosed in the patient's mother, and 2 months later in the eldest son. Subsequently, the results of a molecular genetic study made it possible to verify the diagnosis, since in the gene in exon 3 of VHL, a single nucleotide was replaced in the heterozygous state of C.500 G>A, leading to the replacement of the amino acid p.R167Q. Identification of the VHL gene mutation required genetic counseling of all family members, during which a similar mutation was identified in the younger brother. Surgical treatment is the main method of treating FHL syndrome, but advances in genetic research technologies provide new opportunities for the treatment of tumors associated with this syndrome.

Currently, due to the lack of clear criteria for predicting the aggressive course of pituitary adenomas (APA), the search for diagnostic markers is highly relevant. Genetic markers, among others, may serve as such markers since their identification is possible at early stages of the pathological process.

DICER1 syndrome is a rare monogenic disease with autosomal dominant inheritance. DICER1 protein is involved in the regulation of gene expression by microRNAs. Changes in the expression of DICER1 can be associated with various cancers. A 13,8-year-old girl with a history of embryonal rhabdomyosarcoma (ERMS) of uterine cervix and vagina excised at 6 months of age is presented with a thyroid follicular nodular disease (TFND). Molecular genetic examination revealed a heterozygous pathogenic variant p.Arg1003Ter in the DICER1 gene (NM_030621.4). The presented case emphasizes the importance of molecular genetic diagnosis of DICER1 syndrome in a diagnostic algorithm in the management of patients with TFND and history of malignancy. Considering ERMS of genital tract as a probable component of DICER1 syndrome it is necessary to screen for other manifestations of the disease as well.

Primary hyperparathyroidism (PHPT) is a common endocrine disorder characterized by autonomous secretion of parathyroid hormone by altered parathyroid glands. In most cases PHPT is a sporadic disease, 5-10% of observations are genetically determined syndromal and non-syndromal forms. Studies of families with hereditary forms of PHPT have led to the discovery of key oncosuppressor genes and proto-oncogenes whose somatic mutations underlie the development of many sporadic parathyroid tumors. Another interest in the pathogenesis of primary hyperparathyroidism is studying mechanisms of epigenetic regulation in tumor tissue. In the first part of this review, we will discuss the classification, morphology, and etiology of PHPT. In the second part, we will present a summary of the most important studies using genetic analysis, classified according to the method used.

Pheochromocytoma (PHEO) currently is considered to be malignant due to metastatic potential. One of the most common familial forms of PHEO is multiple endocrine neoplasia syndrome (MEN) type 2. The penetrance of PHEO in MEN2 syndrome is up to 50% of cases. It may be one- or two-sided, but metastases occur extremely rare. The fact that in majority of cases of MEN2 syndrome the source of distant metastases is medullary thyroid carcinoma (MTC) complicates differential diagnosis in case of PHEO metastasis.Isolated cases of PHEO with metastases to the lymph nodes, lungs, liver, bones, brain in MEN2 patients were described. In the available literature, we have found a description of 31 cases of metastatic PHEO in MEN2 syndrome. The available data of those cases is presented as a table in the article.We present a description of a 40-year-old woman with MEN2A syndrome (mutation of the RET proto-oncogene p.Cys634Tyr), with a history of twice-performed surgical treatment of MTC, with daily crises of arterial hypertension accompanied by vegetative symptoms, with a giant bilateral PHEO (up to 200 m on the right and up to 150 mm on the left) with synchronous large metastasis (up to 50 mm) into the pubic bone with the destruction. The patient underwent several surgeries: bilateral adrenalectomy, then a bilateral revision of the neck, removal of the right upper and right lower parathyroid glands, residual thyroid tissue, then resection of the right pubic bone with a tumor.

Cowden disease (Cowden syndrome) refers to PTEN-associated hamartoma tumor syndromes. It arises due to a mutation in the phosphatase and tensin homolog gene, one of the main functions of which is cell cycle regulation. The presence of a mutation in the gene leads to uncontrolled cell growth, and patients have a lifelong increased risk of neoplasms of various degrees of malignancy. This article presents a clinical case of Cowden syndrome with an early debut at the age of 7 years. The combination of macrocephaly (SDS of head circumference >2) with various skin manifestations (facial trichilemmomas, acral keratosis, papillomatous papules) and the presence of benign and/or malignant neoplasms are pathognomonic for Cowden syndrome. Of the malignancies, breast and thyroid cancer, colorectal cancer, renal cell carcinoma, and endometrial cancer are the most common. Thyroid carcinoma has been shown to have an earlier age of manifestation and often occurs already in childhood. This determines the need to screen patients with a proven mutation in the PTEN gene for nodal neoplasms from an early age. If surgical treatment is necessary, thyroidectomy remains preferable due to the frequent recurrence of nodules, as well as the uncertain potential for malignancy due to the low study of thyroid nodules in patients with mutations in the PTEN gene.

In recent years, a large number of studies have been carried out to research molecular genetic abnormalities in ACTH--secreting pituitary tumors. This review presents a comprehensive analysis of exome studies results (germline and somatic mutations, chromosomal abnormalities in corticotropinomas which developed as part of hereditary syndromes MEN 1, 2, 4, DICER1, Carney complex etc., and isolated tumors, respectively) and transcriptome (specific genes expression profiles in hormonally active and inactive corticotropinomas, regulation of cell cycles and signal pathways). Modern technologies (next-generation sequencing - NGS) allow us to study the state of the microRNAome, DNA methylome and inactive chromatin sites, in particular using RNA sequencing. Thus, a wide range of fundamental studies is shown, the results of which allow us to identify and comprehend the key previously known and new pathogenesis mechanisms and biomarkers of corticotropinomas. The characteristics of the most promising molecular genetic factors that can be used in clinical practice for screening and earlier diagnosis of hereditary syndromes and isolated corticotropinomas, differential diagnosis of various forms of endogenous hypercorticism, sensitivity to existing and potential therapies and personalized outcome determination of Cushing`s disease.

DICER1 syndrome is a rare genetic disorder with the progressive development of malignant and non-malignant diseases in childhood. The cause of this syndrome is a dusfunction of the endoribonuclease DICER, which plays an important role in the processing of microRNAs with subsequent regulation of the control of the expression of oncogenes and tumor suppressor genes. Clinical manifestations of dyseropathies is very different and may include both endocrine manifestations - multinodular goiter, differentiated thyroid cancers, ovarian stromal tumors, pituitary blastoma, and non-endocrine formations - pleuropulmonary blastoma, cystic nephroma, pineoblastoma. The presence of somatic mutations of the DICER1 gene is a resultant stage in the pathogenesis of dyseropathies, determining the further path of oncogenesis. At present, DICER1 syndrome is diagnosed extremely rarely, which leads to late detection of the components of the disease in the patient, late diagnosis of neoplasms, lack of family counseling. Diagnosis at the early stages of the disease, the development of screening programs for the management of these patients allows minimizing the risks of developing more malignant, aggressive forms of the disease.

Breast cancer (BC) is a serious disease and is considered an important health problem worldwide. The prevalence of the disease in women according to Rosstat was 64,951 cases in the Russian Federation in 2020 (21.7% among all types of cancer).  Hormone-dependent estrogen receptor-positive (HR+), human epidermal growth factor receptor type 2 negative (HER2-) metastatic breast cancer (mBC) accounts for 70% of all cases.  About 40% of patients with ER+/HER2- mBC have mutations in the PIK3CA gene, leading to hyperactivation of the alpha isoform (p110α) of phosphatidylinositol 3-kinase (PI3K). Hormonal therapy with or without cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor is considered the standard treatment for patients with ER+/HER2- mBC. However, acquired resistance to this therapy remains a problem. Innovative methods for the treatment of breast cancer are the use of targeted therapeutic agents aimed at direct inhibition of the PI3K pathway in combination with hormone therapy. Alpelisib is a PI3Kα-specific inhibitor. Hyperglycemia is the most common side effect of alpelisib treatment. Currently, there is a consensus on the prevention and correction of hyperglycemia in patients receiving therapy with alpelisib, which recommends that before starting therapy, in  order to diagnose carbohydrate metabolism disorders and assess the risk of developing hyperglycemia, determine in all patients: the level of glycated hemoglobin (HbA1c), glucose fasting plasma (FPG), body mass index (BMI). And also to evaluate such risk factors as the presence of a family history of type 2 diabetes mellitus (DM 2), the presence of gestational diabetes in the patient's history, or the fact of the birth of children weighing more than 4 kilograms.Recently, new combinations of drugs have been actively used to treat disorders of carbohydrate metabolism, such as pioglitazone + metformin. This paper discusses the mechanism of action of PI3K inhibitors, new therapeutic combinations and their undesirable effects, and presents therapeutic experience.

We presented the clinical case of neurofibromatosis type 1 (NF-1) associated with pheochromocytoma (PHEO) in a man under 40 years old without family history. The diagnosis of NF-1 was established based on 4 signs of the disease (multiple café au lait macules, scoliotic changes in posture, the presence of multiple neurofibromas, Lisch nodules). The diagnosis of PHEO was determined by a significant increase of free metanephrin/normethanephrin levels in daily urine, a malignant CT phenotype of the right adrenal tumor, and confirmed by pathomorphological study. Genetic tests revealed a new mutation in one of the alleles of NF1 gene, a deletion of a 566 bp gene fragment, including exon 19 with a size of 73 bp. This mutation leads to splicing of exons 18 and 20, frameshift, and termination of protein synthesis. A study of the level of transcription of the genes associated with PHEO (RET, TMEM127, MAX, FGFR, MET, MERTK, BRAF, NGFR, Pi3, AKT, MTOR, KRAS, MAPK) was conducted, a statistically significant decrease in the level of transcription of the KRAS and BRAF genes and increase in the level of transcription of the TMEM127 gene in comparison with control samples have been detected. This case demonstrates the need for timely recognition of NF-1 for further appropriate patient's follow up and show the effectiveness of a multidisciplinary approach to the diagnosis and treatment of NF-1-associated catecholamine-secreting tumors.

Currently, all pheochromocytoma/paraganglioma (PPGLs) are considered malignant due to metastatic potential. Consequently, PPGLs are divided into «metastatic» and «non-metastatic». Metastatic PPGLs can be with synchronous metastasis (metastases appear simultaneously with the identified primary tumor) or metachronous (metastases develop after removal of the primary tumor). The term metastatic PPGLs is not used in the presence of tumor invasion into surrounding organs and tissues, without the presence of distant metastases of lymphogenic or hematogenic origin. It is generally believed that about 10% of pheochromocytomas and about 40% of sympathetic paragangliomas have metastatic potential. On average, the prevalence of PPGLs with the presence of metastases is 15-20%. Risk factors for metastatic PPGLs are widely discussed in the literature, the most significant of which are groups of clinical, morphological and genetic characteristics. The review presents a discussion of such risk factors for metastatic PPGLs as age, localization and type of hormonal secretion of the tumor, the size and growth pattern of the adrenal lesion, the presence of necrosis and invasion into the vessels, the tumor capsule surrounding adipose tissue, high cellular and mitotic activity, Ki-67 index, expression of chromogranin B and S100 protein, the presence of genetic mutations of three main clusters (pseudohypoxia, kinase signaling and Wnt signaling).Over the past two decades, a number of authors have proposed various predictor factors and scales for assessing a probability of metastatic PPGLs. The review contains detailed description and comparison of sensitivity and specificity of such predictor scales as PASS, GAPP, M-GAPP, ASES and COPPS.

Multiple endocrine neoplasia type 1 (MEN1) - is a rare syndrome with an autosomal dominant inheritance pattern caused by a mutation in the tumor suppressor gene (MEN1). Parathyroid involvement is the most common MEN1 manifestation resulting in primary hyperparathyroidism (mPHPT). Data on the prevalence and structure of bone disease in mPHPT compared to sporadic one (sPHPT) are often incomplete and contradictory.

Multiple endocrine neoplasia type 2B (MEN 2B) is a rare variant of hereditary tumor syndromes caused by germinal mutations in the proto-oncogene RET. One of the components of the syndrome is multiple neurinomas, the early detection of  which is not always given due attention. We present a description of the case of MEN 2B, manifested in the first months of life by intestinal ganglioneuromatosis. The disease presented with chronic constipation, including episodes of intestinal obstruction that required repeated surgical interventions. MEN 2B was suspected at the age of 15. At the time of diagnosis, an increase in serum calcitonin levels was noted (1041 pg/ml, norm <9.5 pg/ml), and a node in the thyroid gland was also determined (1,3*1,0*1,2 see, TIRADS 5), subsequently verified as a neoplasm of C-cells. By DNA analysis, a pathogenic variant p.Met918Thr, typical for MEN2 B, was detected in the RET gene. No signs of pheochromocytoma were found at the time of investigation. The patient underwent a thyroidectomy with lymphadenectomy. The difficulties of early diagnosis of sporadic cases of MEN 2B due to the nonspecificity of gastrointestinal manifestations of the disease are discussed.

MEN-1 is a rare autosomal dominant disease caused by mutations in MEN1 gene encoding the menin protein. This syndrome is characterized by the occurrence of parathyroid tumors, gastroenteropancreatic neuroendocrine tumors, pituitary adenomas, as well as other endocrine and non-endocrine tumors. If a patient with the MEN-1 phenotype carry no mutations in the MEN1 gene, the condition considers a phenocopy of syndrome (phMEN1). The possible cause of this changes could be changes in epigenetic regulation, particularly in microRNA expression that might affect menin signaling pathways.

Timely referral of patients for genetic testing to rule out MEN1-associated primary PHPT is important factor in determining treatment strategy and prognosis. In the context of the limited availability of genetic testing, the search for clinical markers indicative of MEN1 gene mutations remains an extremely relevant task.

Peutz-Jeghers Syndrome (Peutz-Jeghers Syndrome, PJS) refers to syndromes of hereditary tumor predisposition and is caused by pathological variants of the STK11 gene, leading to a defect in the synthesis of serine/threonine kinase 11 protein, which acts as a tumor suppressor.Clinical symptoms of the syndrome are combination of hamartomatous polyposis of the gastrointestinal tract and specific skin-mucosal hyperpigmentation. Also, this disease is characterized by a high risk of developing gastrointestinal and extra-intestinal tumors, including benign or malignant tumors of the reproductive system.One of the first signs of the disease in male patients may be prepubertal gynecomastia associated with large-cell calcifying Sertoli cells tumors expressing aromatase. In contrast to from pubertal gynecomastia, prepubertal is extremely rare, and it is often based on pathological causes. Early diagnosis of patients with pre-pubertal gynecomastia, including Peitz-Jaegers syndrome, defines the tactics of gynecomastia management and protocols for monitoring the development of other components of the disease in the future.This article describes two patients with pre-pubertal gynecomastia and Peitz-Jaegers syndrome with different molecular genetic defects: in one case associated with duplication of the STK11 gene site, in the other - with microdeletion of the short arm of chromosome 19 containing this gene.

Functioning pituitary adenomas and pheochromocytomas/paragangliomas are rare in the general population. Pituitary adenomas occur in the familial setting in approximately 5% of cases, whereas pheochromocytomas/paragangliomas can be hereditary in 30-40% of cases. Hereditary syndromes associated with pituitary adenomas include multiple endocrine neoplasia types 1 and 4, familial isolated pituitary adenomas, and Carney complex. Hereditary syndromes associated with pheochromocytomas/paragangliomas and genes, mutations in which predispose to their development, are more numerous. The first clinical descriptions of the co-occurrence of pituitary adenoma and pheochromocytoma/paraganglioma in one patient date back to the mid 20th century, however delineating such a co-occurrence into a particular syndrome («3PAs» (pituitary adenoma, pheochromocytoma, paraganglioma)) was suggested only in 2015. To date, approximately 100 cases of such a co-occurrence have been described in the literature. Mutations in genes encoding subunits of succinate dehydrogenase complex II (SDHx) are revealed in the majority of cases, much less common are mutations in MAX, MEN1 and some other genes. This review summarizes the current information on the «3PAs» syndrome.

Prolactinomas are the most common secreting adenomas of the pituitary. In 20% of cases resistance to dopamine-agonists treatment is observed. Medical therapy resistance causes progression of pathological symptoms of hyperprolactinemia and negative topographic and anatomical changes of prolactinoma. The causes of ineffectiveness of dopamine agonists therapy are not fully understood as well as approaches to managing patients require clarification. Current concepts of resistance are based on the data obtained as a result of surgery or after a period of long-term ineffective therapy. Thus, it is very important to find methods of assessing the sensitivity of prolactin-secreting adenomas to drug therapy before surgical treatment. Genetic and immunohistochemical studies find special place among these methods, making it possible to predict adenoma's response to drug therapy at early diagnostic stage. Obtained results will allow us to form personalized algorithm for managing patients.