** Regional lender Columbia Financial's CLBK.O shares jump 9.3% to $17.79

** In connection with its Northfield Bancorp NFBK.O acquisition, CLBK plans to convert to a fully public company from mutual holding company (MHC) structure through a second-step conversion

** MHCs are mutual institutions that sell a minority of the ownership to the public, with the mutual entity retaining a majority stake

** Some mutuals convert in steps; They sell a minority stake to the public and then later do a so-called second-step offering

** Analysts have previously said CLBK is not well understood and often difficult to value given its MHC structure

** CLBK expects the move to eliminate the "minority discount" in its stock as an MHC

** CLBK stock fell 1.7% in 2025

(Reporting by Arasu Kannagi Basil in Bengaluru)

((ArasuKannagi.Basil@thomsonreuters.com;))