Case 19 Answer

So it’s not normal right?  Lytic lesion in the anterior calcaneous.

This is a classic location for:

1) a unicameral bone cyst: https://radiopaedia.org/articles/unicameral-bone-cyst-1

2) intraosseous lipoma: https://radiopaedia.org/articles/intraosseous-lipoma  (tend to have a somewhat triangular shape in the calcaneous)

I’d probably guess lipoma, but the nice thing is they are both completely benign and there is nothing to do about either so it doesn’t really matter. Both do remember they both can lead to pathologic fractures.