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Resumen La neoplasia endocrina múltiple tipo 2B (MEN 2B) es un síndrome genético poco común, con una prevalencia estimada de 0,9 a 1,6 por millón de individuos y una incidencia de 1,4 a 2,6 por millón de nacidos vivos por año. Es causada por una mutación en el protooncogén RET y se caracteriza por la presencia de carcinoma medular de tiroides (CMT) en el 100 % de los casos, feocromocitoma hasta en el 50 % y características extraendocrinas como un fenotipo marfanoide, alteraciones musculoesqueléticas y dentales, neuromas mucosos, alacrimia y ganglioneuromatosis intestinal difusa con síntomas de dismotilidad esofágica y gastrointestinal. Este síndrome se asocia con una calidad de vida deteriorada y una supervivencia deficiente, debidas principalmente a la agresividad del CMT, enfermedad que usualmente es de aparición temprana o metastásica. El diagnóstico generalmente se realiza de forma tardía, lo cual retrasa el enfoque integral, que incluye tipificación genética, tratamiento quirúrgico temprano del CMT y terapias específicas como inhibidores de tirosina quinasa (ITK) en caso de CMT avanzado. La cirugía es el tratamiento principal y la única posibilidad de cura, aunque el advenimiento de las terapias dirigidas parece estar mejorando la supervivencia libre de progresión en los casos avanzados.

Abstract Multiple endocrine neoplasia type 2B (MEN 2B) is a rare genetic syndrome with an estimated prevalence of 0.9 to 1.6 per million individuals and an annual incidence of 1.4 to 2.6 per million live births. It is caused by a mutation in the RET proto-oncogene and is characterized by the presence of medullary thyroid carcinoma (MTC) in 100% of cases, pheochromocytoma in up to 50%, and extraendocrine features such as a marfanoid phenotype, musculoskeletal and dental abnormalities, mucosal neuromas, alacrimia, and diffuse intestinal ganglioneuromatosis with symptoms of esophageal and gastrointestinal dysmotility. This syndrome is associated with a diminished quality of life and poor survival, primarily due to the aggressiveness of MTC, which often presents at an early or metastatic stage. Diagnosis is often delayed, resulting in a delayed comprehensive approach that includes genetic profiling, early surgical management of MTC, and specific therapies such as tyrosine kinase inhibitors (TKIs) for advanced MTC. Surgery remains the mainstay and the only potential cure, although the advent of targeted therapies appears to improve progression-free survival in advanced cases

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ABSTRACT A 42-year-old male presented with a 4-week history of a mass in the right inferior palpebral conjunctiva close to the punctum. An excisional biopsy of the lesion and histopathological examination revealed that the mass was composed of Schwann cells with thin conical nuclei, fine chromatin, and unnoticeable nucleoli. Immunohistochemically, the spindle cells were diffusely and strongly positive for S100 protein. Neurofilament immunostaining was also positive, which highlighted axons. In light of these findings, the tumor was diagnosed as solitary circumscribed neuroma. A comprehensive evaluation for multiple endocrine neoplasia type 2b was performed. However, no multiple endocrine neoplasia type 2b stigmata and no family history were detected. The diagnosis was therefore finalized as solitary circumscribed neuroma, which is considered as a rare condition. The differential diagnosis is based on the histopathological examination and immunohistochemical evaluation. As the tumor can be related with multiple endocrine neoplasia type 2b, it is essential to systematically investigate for multiple endocrine neoplasia type 2b in such cases.

RESUMO Um homem de 42 anos apresentou uma massa na conjuntiva palpebral inferior direita, próxima ao punctum, com evolução de 4 semanas. Uma biópsia excisional da lesão e o subsequente exame anatomopatológico revelaram que a massa era composta de células de Schwann com núcleos cônicos, croma­tina fina e nucléolos não visíveis. Ao exame imuno-histoquímico, as células fusiformes mostraram-se difusa e fortemente positivas para a proteína S100. A imunocoloração também foi positiva para neurofilamentos e evidenciou os axônios. Considerando esses achados, o tumor foi diagnosticado como um neuroma circunscrito solitário. Procedeu-se uma investigação completa para neoplasia endócrina múltipla tipo 2b, entretanto, estigmas característicos e história familiar não foram detectados. Assim, o diagnóstico foi firmado como neuroma circunscrito solitário, condição rara cujo diagnóstico diferencial baseia-se no exame anatomopatológico e na avaliação imuno-histoquímica. Já que esse tumor pode estar relacionado à neoplasia endócrina múltipla tipo 2b, torna-se essencial, nesses casos, a investigação da neoplasia de forma sistemática.

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ABSTRACT Background: RET proto-oncogene mutations are responsible for familial thyroid medullary carcinoma and multiple endocrine neoplasia (MEN) type 2A and 2B. These syndromes develop specific biomarkers and, in the case of MEN2B, clinically observable stigmas. However, the diagnosis of patients with MEN2B is usually delayed. Because of the close genotype-phenotype correlation, molecular testing is the final approach for the diagnosis to establish preventive care and therapeutic behaviors. Discussion: pM918T is classified as ''highest risk'' for medullary carcinoma with a 50% of lifetime risk for developing pheochromocytoma. Most cases of MEN2B are due to a de novo mutation. Even with the increased risk of developing pheochromocytoma, our 24-year-old patient does not yet present one. Other factors may be involved in the modulation of the phenotype in different populations. Case report: We present the case of a woman diagnosed with a thyroid nodule at the age of nine. She underwent a total thyroidectomy plus radical cervical lymph node dissection, with a diagnosis and initial management of papillary thyroid carcinoma. During the evolution of the disease, she developed pulmonary metastases. At the age of 24, after her first endocrinological evaluation, typical physical manifestations of MEN2B were observed. A re-evaluation of the original thyroidectomy revealed a medullary carcinoma, with positive manifestation CEA and calcitonin. The analysis of RET proto-oncogene identified a de novo mutation in exon 16 (pM918T). Conclusion: The timely diagnosis of MEN2B offers opportunities to make appropriate preventive and therapeutic decisions that may change the natural evolution of the disease and its complications.

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INTRODUÇÃO: Na Neoplasia Endócrina Múltipla tipo 2 (NEM2), o desenvolvimento do Carcinoma Medular de Tireoide (CMT), Feocromocitoma (FEO) e Hiperparatireoidismo primário (HPT) está associado à mutações germinativas ativadoras no proto-oncogene RET. Casos de CMT esporádico podem apresentar mutações somáticas no RET (~40%). A variabilidade fenotípica observada em casos de CMT e FEO familiais associados à NEM2 indica o envolvimento de eventos genéticos adicionais que seriam responsáveis pelas diferenças clínicas observadas nos indivíduos afetados (idade de desenvolvimento, progressão e agressividade do tumor). Outras alterações genéticas no RET como duplas mutações, SNPs e haplótipos específicos podem influenciar na susceptibilidade, agressividade e modulação do fenótipo NEM2. Entretanto, os estudos de outros genes envolvidos no processo da tumorigênese NEM2 ainda estão em andamento. Recentemente foi mostrado que RET ativado controla a expressão de proteínas inibidoras do ciclo celular (p18 e p27). Mutações germinativas no gene p27 foram recentemente associadas à susceptibilidade de tumores neuroendócrinos e estão associadas à síndrome NEM4 (Neoplasia endócrina múltipla tipo 4). Mutações somáticas, inativadoras de p27, são raramente encontradas em vários tipos de tumores. Entretanto, diversos estudos documentaram que a redução na expressão e a sublocalização citoplamática de p27 são controladas por alterações pós-transducionais e/ou epigenéticas. OBJETIVOS: o estudo teve como objetivos avaliar a participação de genes, recentemente associados ao RET ativado, em tumores de pacientes com NEM2 e também verificar se polimorfismos no gene p27 estariam atuando como moduladores de fenótipo em uma grande família com NEM2. CASUÍTICA: foram analisadas 66 amostras tumorais advindas de 36 pacientes com diagnóstico clínico e genético de NEM2 e 28 indivíduos pertencentes a uma grande família com NEM2A-CMTF e mutação C620R no gene RET. MÉTODOS:...

INTRODUCTION: In Multiple Endocrine Neoplasia type 2 (MEN2) the development of medullary thyroid carcinoma (MTC), pheochromocytoma (PHEO) and primary hyperparathyroidism (HPT) are associated with activating germline mutations in RET proto-oncogene. Cases of sporadic MTC may have somatic RET mutations (~ 40%). The phenotypic variability observed in cases with familial MTC/MEN2 and PHEO/MEN2 indicates the probable involvement of additional genetic events that could be responsible for the clinical differences observed in the affected individuals (age development, progression and aggressiveness of the tumor). Other genetic alterations such as RET double mutations, SNPs and specific haplotypes may influence susceptibility, aggressiveness and MEN2 phenotype modulation. However, studies of other genes involved in the tumorigenesis of MEN2 are still in progress. Recently, it was shown that the activated RET controls the expression of cell cycle inhibitory proteins (p18 and p27). Germline mutations in the p27 gene have recently been associated with the susceptibility to neuroendocrine tumors and are associated with the MEN4 syndrome (Multiple endocrine neoplasia type 4). Somatic inactivating mutations p27 are rarely found in many types of tumors. However, several studies have documented that reduced expression and subcellular location of p27 is controlled by post-transductional changes and/or epigenetic factors. OBJECTIVES: This study aimed to evaluate the role of genes recently associated with RET activated in tumors from MEN2 patients and also check whether polymorphisms in the p27 gene would be acting as modulators of phenotype in a large MEN2 family. PATIENTS: We analyzed 66 tumor samples from 36 patients with clinical and genetic diagnosis of MEN2 and from 28 individuals belonging to a large family with FMTC/MEN2A and RET C620R mutation. METHODS: The analyses of somatic p27, p15, p18 and RET...

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