Pericytic tumors are a group of soft tissue neoplasms characterized by a hemangiopericytoma (HPC)-like pattern. The underlying genetic lesion of pericytic neoplasms is still obscure; however, recent advances in molecular pathology have enabled a mechanistic understanding and accurate diagnosis of these tumors. Nevertheless, a subset of unclassified pericytic tumors continues to present substantial diagnostic challenges, potentially impacting clinical decision-making and therapeutic strategies.

Using Ion AmpliSeq Comprehensive Cancer Panel (Thermo Fisher Scientific, Inc.) assay, we searched for HPC-like-associated mutations in a newborn female with a congenital large sublingual unclassified pericytic tumor that recurred after resection and was refractory to chemotherapy treatment. Further analysis of a series of other tumors with distinctive pericytic features was performed via Sanger sequencing and the results were validated via the auto genomics INFINITI^® and Biocartis Assays.

A BRAF V600D mutation was identified in the tumor tissue of the newborn patient. Treatment with the BRAF inhibitor (BRAFi) dabrafenib resulted in a dramatic response and regression of the tumor. Sequencing of 15 additional HPCs revealed the presence of a BRAF V600E mutation in 6 samples.

Our findings suggest that BRAFi may be a useful therapy for unclassified pericytic tumors. Genetic testing for BRAFV600 mutations and other actionable oncogenic variants should be part of the evaluation for pericytic neoplasms, especially with the currently available targeted drug therapies.