Clinicopathological analysis of 2 cases of infant-type hemispheric glioma with ALK gene fusion
Purpose To investigate the clinicopathological features,molecular features,treatment and prognosis of infant-type hemispheric glioma(IHG)with ALK gene fusion of central nervous system.Methods Clinical data of 2 cases of IHG were collected,and the expression of GFAP,Olig2,Syn,NeuN,H3K27M,H3K27me3,H3G34V,H3G34R,ALK,and BRAF were detected using immunohistochemistry.FISH and NGS method was used to detect ALK fusion genes,and relevant liter-atures were reviewed.Results Case 1,a male,15 months old,showed a huge mass in the left frontal and temporal lobe on cranial MRI.Case 2(external hospital consultation),a male,18 months old,was found to have a space occupying lesion in the frontaltemporal lobe.Microscopic examination:in case 1,tumor cells showed diffuse patchy pattern,with small nodular shapes in some areas which separated by fibrous blood vessels.The cell density was high,and the nucleus was round or oval.The mitotic was easy to see,accompanied by bleeding and nec-rosis.In case 2,tumor cells were diffusely distributed,some of them formed pseudorosette around blood vessels and others ar-ranged in bundles.The cells were mild to moderate dysplasia with round or oval nuclei,light staining,small nucleoli,rare mitotic figures,and no microvascular proliferation or necrosis.Immunophenotypes:in case 1 tumor cells were focal positive for GFAP and NeuN,diffuse positive for H3K27me3,ALK(cyto-plasm and cell membrane),and ATRX,p53 positive(30％),negative for Olig2,Syn,H3K27M,H3G34V,H3G34R,and BRAF,Ki67 proliferation index of 20％.In case 2:tumor cells were diffusedly expressed GFAP,ATRX,H3K27me3,ALK(cytoplasm and cell membrane),and Olig2,Syn was weakly positive,NeuN and p53 were negative,and Ki67 proliferation index was 5％.FISH and NGS tests showed ALK gene fusion in both cases,with EML4::ALK fusion in case 1 and LRRFIP1::ALK fusion in case 2.Follow up for 7 months showed that the residual lesion in case 1 had shrunk and was generally in good condition;case 2 lost follow-up.Conclusion The histology of IHG often presents as high-grade gliomas or accompanied by an-aplastic features.The heterogeneity of ALK variants can also manifest as low-grade gliomas,which need to be differentiated from other high-grade gliomas,desmoplastic infantile gangliogli-oma/astrocytoma,ependymoma,etc.
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