Dr. George Crawford -- a general surgeon who focuses on bariatric, colon and minimally invasive procedures in the operating room -- joined "TMZ Live" Friday to discuss the Princess of Wales' announcement ... where she said cancer was found in the aftermath her abdominal surgery.

While Kate didn't get into the details of the exact type of cancer that was found -- Dr. Crawford tells us that, in his professional opinion, it could likely be one of two.

Crawford says that based on Kate's age and other factors ... he speculates that doctors might've discovered either ovarian or uterine cancer -- that's his best guess anyway.

He's not suggesting he knows her exact diagnosis for certain, but Dr. Crawford says his personal experience leads him to land on these two possibilities -- and he even gets into how exactly this may have unfolded.

Dr. Crawford says it's possible that the medical team found something alarming in the middle of the procedure and probably had a biopsy run on it right then and there. Of course, Kate says cancer was discovered after her surgery -- but Dr. Crawford says it's not uncommon to get an answer back fairly quickly ... which can change the course of an entire operation.

He also weighs in on the fact Kate says she just recently started preventative chemo -- which Dr. Crawford says makes sense, seeing how much recovery time is needed for an invasive surgery like the one she seems to have undergone ... and how heavy chemo is on the body.

Kate says she's needed time to recover -- as well as time to address this serious matter with her three young children. The upside ... she says she's getting stronger each day, which sounds promising.

The announcement should hopefully end all the gossip that has poured out of this saga for the past several weeks ... because it's clear, she's dealing with something incredibly urgent.