Immunohistochemical staining for anaplastic lymphoma kinase (ALK) has been described in rhabdomyosarcomas (RMS), especially the alveolar subtype. Previous studies have yielded conflicting results regarding the pattern of staining (nuclear versus cytoplasmic), and there has been no correlation with PAX3-7/FKHR fusion status. This study was undertaken to evaluate ALK receptor protein expression in a large series of RMS; to correlate these results with fusion status; and to investigate the possibility of 2p23 amplification or translocation using fluorescence in situ hybridization (FISH). Sixty-nine cases of RMS were examined and classified as alveolar RMS (ARMS), embryonal RMS (ERMS), or unclassifiable RMS (URMS) subtypes. Anaplastic lymphoma kinase immunohistochemistry was performed using anti-human CD246 antibody; cases were considered positive when more than 50% of cells had moderate or intense cytoplasmic and/or nuclear staining. There were 30 ARMS, 37 ERMS, and 2 URMS subtypes. Reverse transcription-polymerase chain reaction for PAX3/PAX7-FKHR fusion analysis had been done in all cases of ARMS, in 27 of 37 cases of ERMS, and in both URMS cases. Anaplastic lymphoma kinase staining was positive in 16 of 30 ARMS (53%) and 9 of 39 nonalveolar RMS (23%) cases (P < 0.05). Of the 21 ARMS cases with PAX3-FKHR fusion, 10 of 21 (48%) were positive for ALK staining; of the 6 ARMS cases with PAX7-FKHR fusion, 3 of 6 (50%) were positive for ALK staining; and 3 of 3 (100%) of the fusion-negative ARMS were positive with ALK staining. When comparing each of the ARMS subtypes, statistical significance was not reached. All positive cases showed dot-like cytoplasmic staining; nuclear staining was not seen. Of a subset of 6 ALK-positive ARMS submitted for break-apart FISH for the ALK locus, there was no evidence of a translocation; 1 case had ALK amplification and 2 had low-level gains of the ALK gene. We conclude that there is ALK overexpression in RMS, more commonly in ARMS than in ERMS, most likely independent of fusion status. Amplification or upregulation of ALK may underlie ALK protein overexpression.

Glypican-3 (GPC3) is a proteoglycan thought to play an important role during development. Germline GPC3 mutations are seen in the rare Simpson-Golabi-Behmel syndrome (SGBS), which predisposes patients to Wilms tumor, hepatoblastoma, and neuroblastoma. While numerous adult tumors have been evaluated by immunohistochemistry for GPC3, no comprehensive assessment has been done in pediatric tumors. We therefore investigated GPC3 expression in 143 pediatric central nervous system (CNS) tumors and 271 non-CNS tumors. Among non-CNS tumors, GPC3 expression was seen in 9/9 (100%) hepatoblastomas, 4/6 (67%) malignant rhabdoid tumors, 5/13 (38%) Wilms tumors, 11/37 (30%) alveolar rhabdomyosarcomas, and 8/45 (18%) embryonal rhabdomyosarcomas. All 136 neuroblastomas, 14 Ewing sarcoma/primitive neuroectodermal tumors, and 11 synovial sarcomas were immunonegative for GPC3. Among CNS tumors, GPC3 had restricted expression, with positivity in 6/6 (100%) atypical teratoid rhabdoid tumors and 1/4 (25%) craniopharyngiomas. The remaining 136 CNS tumors-23 medulloblastomas, 21 pilocytic astrocytomas, 13 gangliogliomas, 12 ependymomas, 12 glioblastomas, 11 choroid plexus neoplasms, 10 diffuse astrocytomas (grade II/III), 10 meningiomas, 8 dysembryoplastic neuroepithelial tumors, 8 oligodendrogliomas, 3 craniopharyngiomas, 3 germinomas, and 2 neurocytomas-were entirely negative for GPC3. These results showed GPC3 positivity in a number of non-CNS tumors, with no consistent discrimination between tumors that were or were not associated with SGBS. Within the CNS, GPC3 positivity was limited to a small subset of CNS neoplasms and may thus serve as a useful positive diagnostic biomarker (P < 0.0001) in addition to negative INI1/BAF47/SMARCB1 staining to differentiate atypical teratoid rhabdoid tumors from other high-grade pediatric brain tumors.

Esophageal pH monitoring remains a primary diagnostic tool for detecting gastroesophageal reflux disease (GERD). GERD that is refractory to proton pump inhibitor (PPI) medications may be related to CYP2C19 variants. Current PPI dosing practices in children do not take into account CYP2C19 allelic variants, which may lead to underdosing and subsequently to a misperception of PPI therapy failure. We hypothesized that pH probe acid exposure outcomes associate with CYP2C19*17 alleles among children with clinical concern for GERD. We identified a retrospective cohort of 74 children (age range 0.71-17.1 years, mean 8.5, SD 4.6) with stored endoscopic tissue samples and who had also undergone esophageal pH testing while on PPI therapy. These individuals were genotyped for common CYP2C19 alleles and were dichotomized to either CYP2C19*17 allelic carriers without corresponding loss of function alleles as cases vs controls. Associations between pH probe acid exposure outcomes and CYP2C19*17 alleles were investigated. Compared to controls, children who carry CYP2C19*17 alleles without corresponding loss-of-function alleles demonstrated statistically significant longer times with pH < 4 (76.46 vs 33.47 minutes, P = .03); and higher percent of time with pH < 4.0 (5.71 vs 2.67 minutes, P = .04). These findings remained statistically significant using multiple-regression modeling with test duration, PPI dose, and race as confounding variables. PPI therapy in children with *17 alleles may be better optimized with CYP2C19 genotype-guided dosing prior to pH probe testing. Keywords proton pump inhibitor, children, CYP2C19, GERDThe rate of gastroesophageal reflux disease (GERD) diagnoses in children has increased over the past decade with a concomitant rapid increase in the use of proton pump inhibitor (PPI) medications. 1 Esophageal pH monitoring remains the primary diagnostic tool for detecting refractory GERD (not responsive to PPI therapy). 2 When GERD that is refractory to PPI treatment in children is identified in clinical practice, genetic factors related to PPI metabolism are not generally thought to play a role. 3 The efficacy of PPIs to treat GERD and related conditions is closely linked to plasma concentrations. 4 All PPIs except rabeprazole undergo significant metabolism by CYP2C19, and genetic variation in CYP2C19 influences the pharmacokinetics of all PPIs. [5][6][7] The CYP2C19 gene is located on chromosome 10q24.1-q24.3, has 9 exons and is highly polymorphic. 8-10 Several loss-of-function (LOF) alleles (eg, CYP2C19*2 through *9) reduce drug clearance and significantly increase PPI plasma concentrations. Alleles carrying rs12248560 are termed *17, and individuals carrying 1 or 2 such alleles clear PPIs at a higher rate and have lower PPI plasma levels compared to carriers of LOF alleles. 3,[11][12][13] Studies have reported a variable range of 10% to 40% of pediatric and adult GERD patients fail standard doses of PPI and often undergo esophageal pH testing either on or off therapy. 14 Several factors contribu...