Interesting; are these (presumably clotted) blood vessels the threads that another comment mentioned? https://news.ycombinator.com/item?id=40417294
https://sanderspodiatry.com.au/blog/2021/02/23/plantar-warts...
https://www.dovepress.com/dermoscopy-features-of-cutaneous-w...
https://sanderspodiatry.com.au/blog/2021/02/23/plantar-warts...
https://www.dovepress.com/dermoscopy-features-of-cutaneous-w...