Lumpy tile floor in bathroom

[Jotch Bob]

Hi all.

We recently moved into this house and noticed a strange raised patch in the bathroom floor.
The tiles seem well sealed and stable and there is no obvious leak. We rarely use the bath.
I am wondering if this is harmess, like a poorly evened floor, or something more sinister.
The previous owner reports it is longstanding.

Any advice greatly appreciated.

 

[fillyboy]

Looks like 'tile effect' laminate floor that has swollen due to a water leak or spillage, probably historical.