specialist organization; specialized body
Refers to an organization, group, or body that specializes in a particular field or function.
You should consult a specialist organization about this problem.
専門機関 often implies an official or institutional body, while 専門組織 is broader and can include any specialized group or structure.
Compound of 専門 (specialty) and 組織 (organization). The exact historical derivation is uncertain, but the meaning is transparent from its components.