Hard, thick lump in my period

Hi,

this evening I found a hard, thick, fibrous 1cm lump in my period (caught in tissue when I wiped myself), I'm used to having blood clots, and thin uterine lining skin come out, but never have I seen anything like this before, so I'm worried.

I took a photo of it to show the GP.

Could this be a sign of uterine cancer or fibroid or anything like that? It's definitely not a miscarriage as I've not been sexually active.

Any advice?

Thanks,

Natalie