Astrocytoma / Desmoplastic Gamliogliomes (DIA / DIG) - Study of the French Cohort of the Last 20 Years : Clinical, Anatomopathological, Molecular and Radiological Charactersics

Astrocytomas / infantile desmoplastic gangliogliomas (DIA / DIG) are rare brain tumors usually affecting infants. They represent about 0.5% of all pediatric brain tumors. DIA / DIG occurs mainly in the first 2 years of life, with a sex ratio M / F of 1.7 to 1. From a histological point of view, DIA / DIG are neuroepithelial tumors. These tumors may have a purely astrocytic differentiation (DIA) or be composed of tumor cells with astrocytic and neuronal differentiation (DIG). The desmoplastic component is usually adjacent to the meninges and is defined by the increase or modification of connective tissues related to the presence of neoplastic cells with the formation of a collagen-rich extracellular matrix.

Due to their benign biological behavior and favorable clinical course, they are classified in benign tumors, ie grade I according to the WHO classification. However, all tumors called DIA / DIG do not behave in a benign manner. Cases of metastatic cerebrospinal and malignant disorders have been described. It appears that about 40% of DIG cases require additional medical treatment such as chemotherapy, radiotherapy and / or new surgery, and 15% of infants and children with GIDD die from the disease. It is possible that what is grouped within the DIA / DIG is a heterogeneous group of tumors, evolution and prognosis very variable.

The cytogenetic knowledge of DIA / DIG is very limited and is only available on small numbers of cases. Cytogenetic analyzes of several cases of DIG showed normal karyotypes. More recently, a CGH-Array study of 3 cases of DIA / DIG did not find any significant chromosomal gains or losses.

It has been shown, however, that a mutation involving BRAF (BRAF rearrangement or BRAF V600E mutations) was a recurrent element in low grade gliomas, particularly in pediatric patients.

It is also suggested that deregulation of BRAF activity in some DIA / DIG may indicate the importance of the MAPK (mitogen-activated protein kinase) pathway in signaling pathways for DIA / DIG development. However, data on the link between the BRAF gene and DIA / DIG remains very limited. Thus, further studies are needed to study the other members of the MAPK pathway in DIA / DIG (eg PI3K / AKT / mTOR). This could provide new therapeutic possibilities involving targeted therapies specific to the MAPK signaling pathway.

It appears that DIA / DIG does not all behave in a benign manner and some would undergo a malignant transformation that could be due to chromosomal alterations such as, for example, TP53, PI3K. In addition, because of the limited number of cases, it would be interesting to study the characteristics of patients with DIA / DIG in order to study their characteristics and whether there are clinical, pathological, cytogenetic and / Molecular forms between benign and malignant forms.