Masses with Indistinct Margins

Masses with indistinct margins have a portion (or entirety) of the margin with no clear border from the surrounding tissue. The proposed explanation for such morphology is infiltration into the adjacent tissues, blurring the demarcation. Therefore, these masses are frequently concerned for malignancy and are often biopsied for further evaluation. While not an uncommon appearance for malignancy, certain benign entities, such as fat necrosis and pseudoangiomatous stromal hyperplasia (PASH), may also present as masses with indistinct margins.