This comprehensive pathological study of a single patient highlights the complex clinical profile of MAS and illustrates important advances in understanding the characteristics of somatic GNAS1-related pathology across a wide range of affected organs.

Pituitary incidentalomas are a by-product of modern imaging technology. the term 'incidentaloma' is neither a distinct diagnosis nor a pathological entity. Rather, it is a collective designation for different entities that are discovered fortuitously, requiring a working diagnosis based on the input of the radiologist, endocrinologist and often a neurosurgeon. In addition to pathological conditions affecting the pituitary gland, a thorough knowledge of the radiological characteristics of normal variants and technical artifacts is required to arrive at an accurate differential diagnosis. after careful radiological and hormonal evaluation, the vast majority of pituitary incidentalomas turn out to be non-functioning pituitary microadenomas and Rathke's cleft cysts (Rccs). Based on the low growth potential of non-functioning pituitary microadenomas and Rccs, periodic MRI surveillance is currently considered the optimal management strategy. stricter follow-up is required for macroadenomas, as increases in size occur more frequently.

Prolactinomas are the most common hormonally active pituitary tumors and are usually successfully treated with dopamine agonists. A small proportion, however, appears not to respond to such treatment and such cases are termed resistant prolactinomas. Resistance is generally defined as failure to achieve normoprolactinemia and inability to induce tumor shrinkage. Reduced dopamine receptor density on lactotroph cells is currently considered the major underlying mechanism of resistance. Treatment options in resistant cases usually include substitution with another dopamine agonist, increasing the dose of the drug, as well as surgery, radiotherapy, and experimental medical therapies.

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Pituitary adenomas represent a group of functionally diverse neoplasms with relatively high prevalence in the general population. Most occur sporadically, but inherited genetic predisposing factors are increasingly recognized. Familial isolated pituitary adenoma is a recently defined clinical entity, and is characterized by hereditary presentation of pituitary adenomas in the absence of clinical and genetic features of syndromic disease such as multiple endocrine neoplasia type 1 and Carney complex. Familial isolated pituitary adenoma is inherited in an autosomal dominant manner and accounted for approximately 2–3% of pituitary tumors in some series. Germline mutations in the aryl-hydrocarbon interacting protein gene are identified in around 25% of familial isolated pituitary adenoma kindreds. Pituitary adenomas with mutations of the aryl-hydrocarbon interacting protein gene are predominantly somatotropinomas and prolactinomas, but non-functioning adenomas, Cushing disease, and thyrotropinoma may also occur. These tumors may present as macroadenomas in young patients and are often relatively difficult to control. Furthermore, recent evidence indicates that aryl-hydrocarbon interacting protein gene mutations occur in >10% of patients with sporadic macroadenomas that occur before 30 years of age, and in >20% of children with macroadenomas. Genetic screening for aryl-hydrocarbon interacting protein gene mutations is warranted in selected high-risk patients who may benefit from early recognition and follow-up.

Pituitary adenomas are benign intracranial neoplasms that present a major clinical concern because of hormonal overproduction or compression symptoms of adjacent structures. Most arise in a sporadic setting with a small percentage developing as a part of familial syndromes such as multiple endocrine neoplasia type 1 (MEN1), Carney complex (CNC), and the recently described familial isolated pituitary adenomas (FIPA) and MEN-4. While the genetic alterations responsible for the formation of sporadic adenomas remain largely unknown, considerable advances have been made in defining culprit genes in these familial syndromes. Mutations in MEN1 and PRKAR1A genes are found in the majority of MEN1 and CNC patients, respectively. About 15% of FIPA kindreds present with mutations of the aryl hydrocarbon receptor-interacting protein (AIP) gene. Mutations in the CDKN1B gene, encoding p27(Kip)¹ were identified in MEN4 cases. Familial tumours appear to differ from their sporadic counterparts not only in genetic basis but also in clinical characteristics. Evidence suggests that, especially in MEN1 and FIPA, they are more aggressive and affect patients at younger age, therefore justifying the importance of early diagnosis. In this review, we summarize the genetic and clinical characteristics of these familial pituitary adenomas.