Abstract: PIK3CA, which encodes phosphatidylinositol 3 kinase (PI3K) subunit p110a, has been identified as an oncogene. Somatic mutations in the PIK3CA gene cause heterogeneous segmental overgrowth of body tissues, displays as various phenotypes include hemihyperplasia multiple lipomatosis (HHML), megalencephaly-capillary malformation (MCAP), CLOVES syndrome et al. Clinical findings of these syndromes were distinct, but partially overlapping ,and its designations were non-uniformed. The distinct clinical focus of the investigators has led to ascertainment bias in the published literature, complicating a comprehensive assessment of genotype-phenotype correlation analysis. On September 11 and 12, 2013,a two-day workshop convened on the NIH campus in Bethesda, Maryland, discussed emerging clinical and molecular information on the phenotypes caused by PIK3CA somatic mutations. The umbrella term of "PIK3CA-related overgrowth spectrum (PROS)" was agreed upon. Key clinical diagnostic features and criteria for testing were proposed, and testing approaches were summarized. Preliminary recommendations for a uniform approach to assessment of overgrowth and molecular diagnostic testing were determined. Future areas to address including surgical management of overgrowth tissue and vascular anomalies, the optimal approach to thrombosis risk, and the testing of potential pharmacologic therapies. This paper introduced the outcomes of this workshop to provide clarity in research endeavors and to give clinicians useful designations for management, prognostication, and the design of clinical trials of targeted therapies.

Key words: Somatic mosaicism, PIK3CA gene, Fibroadipose overgrowth, Segmental overgrowth, Macrodactyly, CLOVES syndrome, PIK3CA-related overgrowth spectrum (PROS)