Sporadic endocrine tumours and their relationship to the hereditary endocrine neoplasia syndromes

Extraadrenal pheochromocytoma associated to SDHD gene mutation

A familiáris paraganglioma/phaeochromocytoma szindróma autoszomális domináns öröklődésű betegség, amelyet a mitokondrium légzési láncban részt vevő szukcinát dehidrogenáz (SDH) enzim alegységeit kódoló gének mutációi okoznak. A betegség kialakulásában az SDH génmutációk patogenetikai szerepét 2000-ben ismertették elsőként. A szerzők az első genetikailag igazolt hazai beteg kórtörténetét ismertetik, és áttekintik az SDH génmutációk következményeként kialakuló örökletes szindrómák legfontosabb jellemzőit. Esetismertetés: A 33 éves férfit magas vérnyomás, verejtékezés és palpitáció miatt vizsgálták. A laboratóriumi vizsgálatok megnövekedett vizeletnoradrenalin- és -normetanephrin-ürítést, a radiológiai képalkotó vizsgálatok az aorta hasi szakasza előtt 3,5 cm átmérőjű szolid daganatot mutattak ki. A daganat műtéti eltávolítása után a beteg panaszmentessé vált, a szövettani vizsgálat extraadrenalis phaeochromocytomát igazolt. A beteg családi anamnézise nem, de fiatal életkora felvetette örökletes daganat lehetőségét. A perifériás vér DNS-mintájában az SDHD gén nukleotidszekvencia-analízise kereteltolódással járó heterozigóta c. 148-149 insA mutációt igazolt, amely csonkolt fehérjét eredményez. Családvizsgálattal a mutációt a tünetmentes édesapában is kimutatták, míg a beteg édesanyja és testvére nem hordozta a mutációt. Következtetés: A bemutatott eset az első hazai beteg, akiben az extraadrenalis phaeochromocytoma hátterében genetikai vizsgálattal SDHD génmutációt mutattak ki. A családfavizsgálat felvetette a betegségre jellemző genomiális imprinting jelenség lehetőségét.

RET signaling in endocrine tumors: delving deeper into molecular mechanisms

The rearranged during transfection (RET) proto-oncogene encodes a receptor tyrosine kinase that is implicated in the development of endocrine tumors of the thyroid and adrenal glands. In humans, activating RET mutations are found in the inherited cancer syndrome multiple endocrine neoplasia 2 and in sporadic medullary and papillary thyroid carcinomas. The specific type and location of RET mutations are strongly correlated with the disease phenotype and have both diagnostic and prognostic value. Recent advances in the molecular characterization of the RET receptor and its mutants have begun to define the mechanisms underlying the transforming ability of the different RET mutant forms. This information has revealed key functional features of these mutant proteins that distinguish the different clinically recognized mutations and provide clues as to the functional origins of the phenotypes associated with specific RET mutations. The elucidation of molecular mechanisms involved in RET-mediated transformation is a key step in the development of much needed therapeutics that target RET's oncogenic properties. Recent advances have begun to provide a deeper understanding of the receptor's function, and dysfunction, in human tumors that may guide this process.

RET and neuroendocrine tumors

The RET proto-oncogene encodes a receptor tyrosine kinase that is a main component of the signaling pathway activated by the glial cell line-derived neurotrophic factor family ligands. Gene targeting studies revealed that signaling through RET plays a crucial role in neuronal and renal organogenesis. It is well-known that germline mutations in RET lead to the human inherited diseases, multiple endocrine neoplasia type 2 (MEN 2) and Hirschsprung's disease, and that somatic rearrangements of RET cause papillary thyroid carcinoma. Due to marked advances in understanding of the molecular mechanisms of the development of MEN 2, a consensus on MEN 2 management associated with RET status is being reached and currently put into general use as a guideline. In this review, we summarize progress in the study of RET from bench to bedside, focusing on pathophysiology of neuroendocrine tumors.

The finding of a somaticdeletion in RET exon 15 clarified the sporadic nature of amedullary thyroid carcinoma suspected to be familial

Medullary thyroid carcinoma (MTC) occurs both sporadically and in the autosomal dominantly inherited multiple endocrine neoplasia (MEN) type 2 syndromes. The distinction between both is important for future clinical management. We report a family initially described as a familial MTC by pentagastrin stimulation test and clinical outcome, in which we found a 12 bp deletion within the catalytic domain of the protooncogene RET in the index case tumor alone. Linkage study suggests that it is a sporadic MTC. Therefore, in view of these results, in kindred with just one MTC case, borderline pentagastrin test values must be carefully assessed. In addition, this and other mutations can help us to understand some features about domains that play an important role in the normal function of this tyrosine kinase receptor and involved in MTC.

Neuroendocrine tumor markers

Tumor markers used in the diagnosis and follow-up of patients with neuroendocrine tumors are in most instances not specific for a given tumor and circulate under normal conditions in the serum, making their use as an early diagnostic tool difficult (low sensitivity). By combining hormone measurements with tissue responsiveness, demonstrations of inappropriate secretions of PTH, insulin, and gastrin during hypercalcemia, hypoglycemia, and hyperacidity, respectively, become highly sensitive and specific diagnostic tests. The application of polyclonal antibodies in RIAs of hormones, such as ACTH, insulin, and gastrin, increase the diagnostic level of hormone measurements in patients with neuroendocrine tumors. Other markers, such as chromogranin A, neuron-specific enolase, and alpha-subunit, as well as peptide receptor visualization, are of increasing importance in the diagnosis and follow-up of neuroendocrine and non-neuroendocrine tumors.