Castle Biosciences Inc. is acquiring gastrointestinal (GI) diagnostics company Cernostics Inc. in a transaction valued up to $80 million. The deal marks a move from Castle’s focus on dermatology diagnostics to include GI disorders and could expand its estimated U.S. total addressable market by approximately $1 billion, the company said. Shares of Castle Biosciences (NASDAQ:CSTL) jumped 7.8% to close at $67.58 on Tuesday Oct. 19.