Diane Sawyer Mum's the Word On Bruce Jenner Interview

2/5/2015 7:05 AM PST

Diane Sawyer -- Mum's the Word on Bruce Jenner Interview (VIDEO)

EXCLUSIVE

Diane Sawyer was in no mood to spill the beans about what appears to be her big scoop with Bruce Jenner

Our photog got Diane leaving her home in NYC Thursday ... and when he mentioned the interview, you can see Sawyer pick up the pace, scurrying to her SUV.

TMZ broke the story ... Bruce's transition into becoming a woman will be chronicled in a docuseries that will air as early as May. Production and Jenner family sources tell us it will NOT premiere until "Keeping Up with the Kardashians" Season 10 has fully aired. 

The Sawyer interview is tricky. We're told Bruce wants to maintain enough mystery for his docuseries but use other media promotionally.