Avaliação da fisiopatologia do astrocitoma pilocítico em adultos: análise histopatológica e imuno-histoquímica
Data
2022-11-30
Autores
Santino, Samara Ferreira 
Orientadores
Malinverni, Andréa Cristina de Moraes
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
O astrocitoma pilocítico é um tumor cerebral de crescimento lento, que representa 5% de todos os gliomas e se desenvolve com mais frequência no cerebelo (42 a 60%), mas também pode surgir em outras áreas neurais, como: via óptica ou hipotálamo (9 a 30%); tronco cerebral (9%); medula espinal (2%). Na população pediátrica, este tumor constitui a segunda causa mais comum de neoplasias e, por outro lado, em adultos é frequentemente raro, provavelmente devido à sua agressividade nestes indivíduos. Estudos revelam que a origem do astrocitoma pilocítico é caracterizada por uma fusão entre o gene BRAF e o locus KIAA1549, e a aplicação da técnica de imuno-histoquímica para a análise da expressão da proteína BRAF pode ser uma ferramenta de grande valia para fins diagnósticos. Devido à relativa raridade dessa doença em indivíduos adultos, poucas são as publicações sobre as estratégias de diagnóstico e tratamento mais eficazes para este tumor. O objetivo geral deste estudo foi analisar as características histopatológicas e imuno-histoquímicas do astrocitoma pilocítico nestes pacientes. Para isso, foi realizado um estudo retrospectivo de pacientes com idade superior a 18 anos com diagnóstico de astrocitoma pilocítico no Departamento de Patologia da UNIFESP/EPM, no período de 1991 a 2015. Para definir a positividade de BRAF na análise imuno-histoquímica utilizou-se como critério, no mínimo três campos consecutivos com mais de 50% de imunomarcação e, assim, inferiu-se que os 7 casos analisados foram considerados positivos para o marcador citoplasmático BRAF V600E. A análise histopatológica associada à imunomarcação de BRAF é de suma importância como método diagnóstico nestes casos. Todavia, estudos moleculares futuros serão necessários tanto para melhor entendimento da agressividade e prognóstico deste tumor quanto para pesquisas que envolvam terapias específicas para o astrocitoma pilocítico em adultos.
Pilocytic astrocytoma is a central nervous system tumor of slow growth, which represents 5% of all gliomas and most often develops in the cerebellum (42 to 60%), but can also arise in other neural areas, such as the optic pathway or hypothalamus (9 to 30%); brainstem (9%); spinal cord (2%). In the pediatric population, this tumor is the second most common cause of neoplasms and, on the other hand, in adults, it is often rare, probably due to its aggressiveness in these individuals. Studies reveal that the origin of pilocytic astrocytoma is characterized by a fusion between the BRAF gene and the KIAA1549 locus, and the application of the immunohistochemistry technique for the analysis of BRAF protein expression can be a valuable tool for diagnostic purposes. Due to the relative rarity of this disease in adults, there are few publications on the most effective diagnostic and treatment strategies for this tumor. The general objective of this study was to analyze the histopathological and immunohistochemical characteristics of pilocytic astrocytoma in these patients. For this, a retrospective study of patients aged over 18 years with a diagnosis of pilocytic astrocytoma was carried out at the Department of Pathology of UNIFESP/EPM, from 1991 to 2015. In order to define BRAF positivity in the immunohistochemical analysis, at least three consecutive fields with more than 50% immunostaining were used as criteria and, thus, it was inferred that the 7 cases analyzed were considered positive for the cytoplasmic marker BRAF V600E. Histopathological analysis associated with BRAF immunostaining is of paramount importance as a diagnostic method in these cases. However, future molecular studies will be necessary both for a better understanding of the aggressiveness and prognostic of this tumor and for research involving specific therapies for pilocytic astrocytoma in adults.
Pilocytic astrocytoma is a central nervous system tumor of slow growth, which represents 5% of all gliomas and most often develops in the cerebellum (42 to 60%), but can also arise in other neural areas, such as the optic pathway or hypothalamus (9 to 30%); brainstem (9%); spinal cord (2%). In the pediatric population, this tumor is the second most common cause of neoplasms and, on the other hand, in adults, it is often rare, probably due to its aggressiveness in these individuals. Studies reveal that the origin of pilocytic astrocytoma is characterized by a fusion between the BRAF gene and the KIAA1549 locus, and the application of the immunohistochemistry technique for the analysis of BRAF protein expression can be a valuable tool for diagnostic purposes. Due to the relative rarity of this disease in adults, there are few publications on the most effective diagnostic and treatment strategies for this tumor. The general objective of this study was to analyze the histopathological and immunohistochemical characteristics of pilocytic astrocytoma in these patients. For this, a retrospective study of patients aged over 18 years with a diagnosis of pilocytic astrocytoma was carried out at the Department of Pathology of UNIFESP/EPM, from 1991 to 2015. In order to define BRAF positivity in the immunohistochemical analysis, at least three consecutive fields with more than 50% immunostaining were used as criteria and, thus, it was inferred that the 7 cases analyzed were considered positive for the cytoplasmic marker BRAF V600E. Histopathological analysis associated with BRAF immunostaining is of paramount importance as a diagnostic method in these cases. However, future molecular studies will be necessary both for a better understanding of the aggressiveness and prognostic of this tumor and for research involving specific therapies for pilocytic astrocytoma in adults.