Which bodily mass is most likely to change its hardness? (Read Please!)?!

Is there a such thing as a bodily mass (like an unknown lump in your body, such as a lipoma, cyst, cancerous mass, etc!.) that can change from soft to hard and hard to soft again!? Back and forth at seemingly random times!? Are any of these masses (or another kind of mass) known to change in their hard/firmness!? I don't just mean harden gradually!. I mean change back and forth if even slightly!. This is just out of curiosity!. Thank you!.Www@Answer-Health@Com

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