Stupid question about cutting a bookshelf

[WhileMyMeringueGentlyWeeps]

Hi, I really don't know if I'm being daft here and neither google or YouTube are clarifying that.
I want to use an Ikea billy bookshelf unit in my bathroom as toiletry storage but the corner has a pipe about 18 inches from the floor running around the wall. It's a waste pipe from the basin so it's quite a wide diameter. Maybe an inch and a quarter or an inch and a half.
Can I just cut a curved section out of the back of the unit so it will stand flush with the wall or will it fall to bits?

Look on the IKEA hackers website.
Will what you cut be visible or against a wall? A lot of IKEA furniture is like honeycomb inside. It can be cut (through tape works well) but you won't necessarily have a neat finish.

Should be fine, just check the backboard is properly nailed in. We cut lots of bits off of our Billy's to fit them round things and never had a problem.

Yay I'm not completely thick!
Good tip about the tape. The side will be visible so I guess a fine blade in the jigsaw.

My DH cut a section out of the back base of a Billy bookcase to accommodate Victorian depth skirting- and then a shaped bit to go round a dado rail - which remained visible - so we could fit it on the landing in a tight space.

It worked really well and didn't fall apart at all (although it is just chipboard under the veneer, it still lasted for years like that).

We've now got it in a different house. With the slightly odd shaped bits missing!!

Isn't the problem that the cut unit will be in a bathroom? So likely to get damp in the exposed edge which - if mdf or similar could just start to dissolve?

I'd be tempted to try and seal that cut edge with something to try and prevent that. Or be prepared to replace the unit every couple of years or so.