Most companies already have a preferred law firm/attorney or in house counsel. Your business attorney is likely perfectly qualified to review and advise on your office lease or real estate contract. For efficiency purposes however, sometimes it is in your best interest to seek out an expert in real estate transactional work in the specific market you are considering. Somebody who is already intimately familiar with the clauses in your real estate contract and who already knows the industry standards can likely do your work faster (and for less $$).
There is a plethora of really good real estate attorneys in Seattle. Below are a few whom I have done business with or who were recommended by other industry professionals I have surveyed.
Here is a list of their contact information for quick reference.