Brainstem Low-Grade Gliomas in Children-Excellent Outcomes With Multimodality Therapy.

Safe maximal surgical resection is the initial treatment of choice for pediatric brainstem low-grade gliomas. Optimal therapy for incompletely resected tumors or that progress after surgery is uncertain. We reviewed the clinical characteristics, therapy, and outcomes of all children with nontectal brainstem low-grade gliomas treated at the University of Michigan between 1993 and 2013. Median age at diagnosis was 6 years; histology was confirmed in 23 of 25 tumors, 64% were pilocytic astrocytoma. Nineteen patients underwent initial tumor resection; 14/19 received no upfront adjuvant therapy. Eight patients in the study had progressive disease; 5 initially resected tumors received chemotherapy at tumor relapse, all with partial or complete radiographic responses. Ten-year progression-free survival is 71% and overall survival, 100%. This single-institution retrospective study demonstrates excellent survival rates for children with brainstem low-grade gliomas. The efficacy of the well-tolerated chemotherapy in this series supports its role in the treatment of unresectable or progressive brainstem low-grade gliomas.

Activating KRAS mutations are characteristic of oncocytic sinonasal papilloma and associated sinonasal squamous cell carcinoma.

Oncocytic sinonasal papillomas (OSPs) are benign tumours of the sinonasal tract, a subset of which are associated with synchronous or metachronous sinonasal squamous cell carcinoma (SNSCC). Activating EGFR mutations were recently identified in nearly 90% of inverted sinonasal papillomas (ISPs) - a related tumour with distinct morphology. EGFR mutations were, however, not found in OSP, suggesting that different molecular alterations drive the oncogenesis of these tumours. In this study, tissue from 51 cases of OSP and five cases of OSP-associated SNSCC was obtained retrospectively from six institutions. Tissue was also obtained from 50 cases of ISP, 22 cases of ISP-associated SNSCC, ten cases of exophytic sinonasal papilloma (ESP), and 19 cases of SNSCC with no known papilloma association. Using targeted next-generation and conventional Sanger sequencing, we identified KRAS mutations in 51/51 (100%) OSPs and 5/5 (100%) OSP-associated SNSCCs. The somatic nature of KRAS mutations was confirmed in a subset of cases with matched germline DNA, and four matched pairs of OSP and concurrent associated SNSCC had concordant KRAS genotypes. In contrast, KRAS mutations were present in only one (5%) SNSCC with no known papilloma association and none of the ISPs, ISP-associated SNSCCs, or ESPs. This is the first report of somatic KRAS mutations in OSP and OSP-associated SNSCC. The presence of identical mutations in OSP and concurrent associated SNSCC supports the putative role of OSP as a precursor to SNSCC, and the high frequency and specificity of KRAS mutations suggest that OSP and OSP-associated SNSCC are biologically distinct from other similar sinonasal tumours. The identification of KRAS mutations in all studied OSP cases represents an important development in our understanding of the pathogenesis of this disease and may have implications for diagnosis and therapy. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

High-Frequency Targetable EGFR Mutations in Sinonasal Squamous Cell Carcinomas Arising from Inverted Sinonasal Papilloma.

Inverted sinonasal papilloma (ISP) is a locally aggressive neoplasm associated with sinonasal squamous cell carcinoma (SNSCC) in 10% to 25% of cases. To date, no recurrent mutations have been identified in ISP or SNSCC. Using targeted next-generation sequencing and Sanger sequencing, we identified activating EGFR mutations in 88% of ISP and 77% of ISP-associated SNSCC. Identical EGFR genotypes were found in matched pairs of ISP and associated SNSCC, providing the first genetic evidence of a biologic link between these tumors. EGFR mutations were not identified in exophytic or oncocytic papillomas or non-ISP-associated SNSCC, suggesting that the ISP/SNSCC spectrum is biologically distinct among sinonasal squamous tumors. Patients with ISP harboring EGFR mutations also exhibited an increased progression-free survival compared with those with wild-type EGFR. Finally, treatment of ISP-associated carcinoma cells with irreversible EGFR inhibitors resulted in inactivation of EGFR signaling and growth inhibition. These findings implicate a prominent role for activating EGFR mutations in the pathogenesis of ISP and associated SNSCC and rationalize consideration of irreversible EGFR inhibitors in the therapy of these tumors.