Why are these mushroom stems leaving a long, skinny fiber behind on the cap?

Question

I was pulling the stems out of some mushroom caps today - we save the stems and make broth out of them - when I discovered that some stems weren't coming out all the way. Have a look:

Mushroom fanatics out there: Any idea what causes this? Is there something wrong with these mushrooms? Am I being paranoid because I just read this question?

Answer

Jefromi's comment is spot on. I wouldn't be paranoid. The stem probably just didn't feel like coming out and hung on the head. This is completely normal and unless you picked these mushrooms yourself, I would never worry about that.

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