Case 8 Answer

Hamartoma. This large mass contains mixed fat and glandular tissue with well-defined margins. This is the appearance of a hamartoma (also known as a fibroadenolipoma). Sometimes referred to as a "breast within a breast," sometimes a "slice of salami", this finding is benign, and does not need further workup.

The other fat-containing masses should not be confused, because each has a distinctive appearance on mammography.  See the related cases below.

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