NTRK Fusions Identified in Pediatric Tumors: The Frequency, Fusion Partners, and Clinical Outcome.

PURPOSE: Neurotrophic tyrosine receptor kinase (NTRK) fusions have been described as oncogenic drivers in a variety of tumors. However, little is known about the overall frequency of NTRK fusion in unselected pediatric tumors. Here, we assessed the frequency, fusion partners, and clinical course in pediatric patients with NTRK fusion-positive tumors. PATIENTS AND METHODS: We studied 1,347 consecutive pediatric tumors from 1,217 patients who underwent tumor genomic profiling using custom-designed DNA and RNA next-generation sequencing panels. NTRK fusions identified were orthogonally confirmed. RESULTS AND DISCUSSION: NTRK fusions were identified in 29 tumors from 27 patients with a positive yield of 2.22% for all patients and 3.08% for solid tumors. Although NTRK2 fusions were found exclusively in CNS tumors and NTRK1 fusions were highly enriched in papillary thyroid carcinomas, NTRK3 fusions were identified in all tumor categories. The most canonical fusion was ETV6-NTRK3 observed in 10 patients with diverse types of tumors. Several novel NTRK fusions were observed in rare tumor types, including KCTD16-NTRK1 in ganglioglioma and IRF2BP2-NTRK3 in papillary thyroid carcinomas. The detection of an NTRK fusion confirmed the morphologic diagnosis including five cases where the final tumor diagnosis was largely based on the discovery of an NTRK fusion. In one patient, the diagnosis was changed because of the identification of an ETV6-NTRK3 fusion. One patient with infantile fibrosarcoma was treated with larotrectinib and achieved complete pathologic remission. CONCLUSION: NTRK fusions are more frequently seen in pediatric tumors than in adult tumors and involve a broader panel of fusion partners and a wider range of tumors than previously recognized. These results highlight the importance of screening for NTRK fusions as part of the tumor genomic profiling for patients with pediatric cancer.

A Rare BSEP Mutation Associated with a Mild Form of Progressive Familial Intrahepatic Cholestasis Type 2

ABSTRACT Progressive Familial Intrahepatic Cholestasis type 2 (PFIC2) is a rare cholestatic disorder diagnosed in infancy or childhood that can lead to severe hepatic fibrosis and liver failure. Mutations in the ABCB11 gene result in a deficiency of the bile salt export protein (BSEP) and accumulation of bile inside the hepatocytes. Hepatocellular carcinoma is another condition associated with severe forms of deletion mutations in the ABCB11 gene. Treatment options including ursodeoxycholic acid biliary diversion have mixed outcomes and some patients require liver transplantation. Here, we describe two siblings with an extremely mild form of PFIC2 inherited from heterozygous parents. The elder sibling had acute liver failure at the age of six months and both siblings had pruritus, cholestasis, coagulopathy and fat-soluble-vitamin deficiencies in infancy but have been asymptomatic past infancy. Genetic testing of the siblings revealed that each were compound heterozygotes for two missense mutations of the ABCB11 gene: p.C68Y and p.R832H. Medical treatment typical for PFIC2 has not been necessary for either patient. This is the first report of these variants following a mild course in two affected patients.(AU)

A Rare BSEP Mutation Associated with a Mild Form of Progressive Familial Intrahepatic Cholestasis Type 2.

Progressive Familial Intrahepatic Cholestasis type 2 (PFIC2) is a rare cholestatic disorder diagnosed in infancy or childhood that can lead to severe hepatic fibrosis and liver failure. Mutations in the ABCB11 gene result in a deficiency of the bile salt export protein (BSEP) and accumulation of bile inside the hepatocytes. Hepatocellular carcinoma is another condition associated with severe forms of deletion mutations in the ABCB11 gene. Treatment options including ursodeoxycholic acid biliary diversion have mixed outcomes and some patients require liver transplantation. Here, we describe two siblings with an extremely mild form of PFIC2 inherited from heterozygous parents. The elder sibling had acute liver failure at the age of six months and both siblings had pruritus, cholestasis, coagulopathy and fat-soluble-vitamin deficiencies in infancy but have been asymptomatic past infancy. Genetic testing of the siblings revealed that each were compound heterozygotes for two missense mutations of the ABCB11 gene: p.C68Y and p.R832H. Medical treatment typical for PFIC2 has not been necessary for either patient. This is the first report of these variants following a mild course in two affected patients.