[Expression of anaplastic lymphoma kinase clone 1A4 in pediatric medulloblastoma and its significance].

Objective: To investigate the immunohistochemical staining of anaplastic lymphoma kinase (ALK; clone 1A4) in pediatric medulloblastoma (MB). Methods: Molecular subtyping was performed based on the NanoString and sequencing techniques for 44 pediatric MB cases at Children's Hospital, Zhejiang University School of Medicine from 2014 to 2017. ALK expression was detected with EnVision immunhistochemistry using ALK clone 1A4 on whole section. Statistical analyses were performed to evaluate the correlation of protein expression with molecular subgroups. Results: The age ranged from 0.5 to 13.0 years with an average age of 5.8 years. There were 28 males and 16 females, and 31 classic, 5 desmoplastic nodular, 3 extensive nodular and 5 large cell/anaplastic MBs. Except three cases was unable classified, 41 MBs were classified into the four molecular groups: 5 in WNT group, 12 in SHH group, 9 in Group 3 and 15 in Group 4. Thirteen of 44 MB cases were positive staining for ALK, and the positive rate was 29.5%. Six cases were strong reaction, and 7 cases were weak. The expression of ALK at the protein level was associated with the WNT group (P<0.01). The characteristic perinuclear dot-like staining was only showed in WNT group. Conclusions: The ALK immunhistochemistry using antibody clone 1A4 is a useful marker for the molecular subgroup detection of MB. The strong staining and perinuclear dot-like staining indicate as WNT group.