We identified activating mutations in PIK3CA and genes involved in MAPK signaling, including FGFR3, KRAS, HRAS, and BRAF. Common hotspot mutations, such as FGFR3 R248C and PIK3CA E342K and E345K, were found at high allele fractions in several specimens and have been described in other benign cutaneous neoplasms. The gene discussed is PIK3CA; the disease is benign neoplasm of skin.