Is this the Alien Pre-chest burst?

I always felt that the little circular object in the screen was the developing xenomorph embryo, and Ash is watching over its growth like a mother hen protecting her brood--hence he shuts the screen off when Ripley shows up.

Ash is one creepy bugger. Just watching the chestburster develop inside Kane, and then when Kane's eating his last supper Ash is still eyeballing the poor guy, just waiting for the show to start.

In deleted dialogue Ash said there was a 'stain' on Kane's lung, indicating it was blocking the scanner.

It's possible it was an embryonic Alien.  I like that it's ambiguous.

Indeed.. we all know the Xenomorph Face Hugger implants a Embryo well this is what most assumed... the Alien Covenant Creature Design Team T-Shirts showed a break down of the Face Hugger Anatomy to a degree and indeed seemed to show that indeed a Embryo is implanted.

Most Life on Earth (Birds, Fish, Reptiles, Amphibians and Mammals) all have a early first stage Embryo Stage that is nearly identical.

So maybe a Xeno Embryo is not massively different.

I always thought the way Ash was acting strange the whole time indicated that he knew it was fixing to be "alien-busting-out-some-poor-schelp time..."

This is one one the foundation truths to my premise that Weyland has known about the black goo and its offspring a long time...

@S.M. Ripley or Dallas later confronts Ash about claiming that the "tumor" was a "stain blocking the scanner", knowing he was using that excuse as a cover-up. He knew that "stain" was a xeno in vivo...

Kane is a mammalian host, so I think the embryo simply inherited the embryonic design from his DNA. 

Good post, upvoted!

"@S.M. Ripley or Dallas later confronts Ash about claiming that the "tumor" was a "stain blocking the scanner", knowing he was using that excuse as a cover-up. He knew that "stain" was a xeno in vivo..."

The stain was visible to anyone, so I'm not sure how he could've used it as a cover up?

I think Ripley didn't say anything about the what was on the screen because Ash shut it off before she could see it. It might have been a whole other thing if she asked him to turn the monitor back on.

She could see it because she asks Ash what it is.  He says he doesn't know yet and turns it off.

SM- correction. She apparently saw it. It seems like she was more focused on getting on his case for letting it in than viewing the screen.