At the Meguro Parasitological Museum [1], they have an 8 meter long tapeworm [2] extracted from a human. Yes, that is an extreme example and still less mass than a person, but they can get large.

[1] https://www.kiseichu.org/e-top

[2] Visible in the tall blue case here: https://static.wixstatic.com/media/079dcd_843c7597ef244423aa...