Shearman & Sterling said Wednesday that it will stay put at its longtime Manhattan address for the next two decades and plans to give the space an "innovative and eco-friendly" facelift over the next three years.

The firm said it had signed a 20-year lease for 338,000 square feet at 599 Lexington Ave., a 47-story Boston Properties building at the intersection of 53rd Street that has been Shearman's home since the 1980s. Its decision to remain in the Midtown East area contrasts with moves by other big firms to new office towers in the Hudson Yards neighborhood on Manhattan's West Side.

"There were so many compelling options and we thought about a number of them, and Hudson Yards was among them," said Lisa Brill, Shearman's managing partner for the Americas, in an interview. "We were really focused on finding the best option for us and for our people."

Brill wouldn't comment on the terms of the deal. A real-estate industry source told the New York Law Journal that Shearman's starting rent on the space is $79 per square foot.

Shearman said it would start renovating its space this summer and has plans for its conference rooms, "client huddles," a library and a cafe.

Renovations should be finished by Winter 2023, the firm said, with Perkins and Will as the firm's architect. The firm said it will continue to occupy most of its current floors. Brill said she couldn't immediately provide details about how the renovation would proceed. 

The firm said its Midtown location is well-served by transit and amenities and close to clients' offices. Landlord Boston Properties, which also owns two adjacent buildings and refers to them as its "Midtown campus," said it would be enhancing the area with "restaurants, amenities and entertainment" in the base of 601 Lexington.

In Boston Properties' most recent annual report, Shearman was described as its 10th-largest tenant, with 472,144 square feet across its portfolio. The firm's San Francisco offices are also in a Boston Properties building, at 535 Mission St.

The news comes as several prominent firms have moved or made plans to move to the Related Cos. Hudson Yards' development and other new office towers on the West Side.

Milbank, Cooley and Boies Schiller Flexner have moved to 55 Hudson Yards, while Debevoise & Plimpton recently announced that it would move into a nearby building called The Spiral in 2022. Other West Side movers include Skadden, Arps, Slate, Meagher & Flom, which has plans to move to One Manhattan West, and Cravath, Swaine & Moore, which is slated to move into Two Manhattan West.