Benign Breast Lesions That Mimic Cancer: Determining Radiologic-Pathologic Concordance

Julia Mario, BA; Shambhavi Venkataraman, MD; Vandana Dialani, MD; Priscilla J. Slanetz MD, MPH


Appl Radiol. 2015;44(9):28-32. 

In This Article

Fat Necrosis

Fat necrosis is a nonsuppurative inflammatory process secondary to accidental or surgical trauma (eg, blunt trauma, biopsy, lumpectomy, reduction, augmentation, reconstruction, radiation therapy) and is characterized histologically by foamy histiocytes, lipid-laden macrophages, inflammatory cells with peripheral fibrosis and necrosis. It may present as a painless palpable mass or may be discovered incidentally on imaging.

Fat necrosis has variable imaging appearances. The mammographic appearance of fat necrosis ranges from a lucent mass, ill-defined asymmetry, focal mass with microlobulated, ill-defined or spiculated margins, to grouped microcalcifications (Figure 1A,B, D).[16,17] The amount of fibrosis in the lesion determines its mammographic appearance. Sonographically, fat necrosis can present as a cyst, complex cystic or a solid mass with well circumscribed, ill-defined or spiculated margins and architectural distortion of the surrounding tissues (Figure 1c, e).[18] On MRI, fat necrosis is characterized by fatty signal intensity mass, often containing a fat-fluid level with variable enhancement following contrast. Other MRI appearances include a solid irregular mass with variable signal intensity on T1- and T2-weighted images, and intense enhancement with Type-II or Type-III kinetics.[19] Correlation with clinical history often aids in diagnosis; however, biopsy may be necessary to confirm the diagnosis.

Figure 1.

Fat necrosis. (A) A 52-year-old woman with no personal or family history of cancer, presented for a screening mammogram. Mammogram showed a well-circumscribed mass with microcalcifications (arrow). Ultrasound evaluation (not shown) showed an oval mass with angular margins and microcalcifications. (B) A 56-year-old woman presented with firm palpable right breast mass after a car accident. Craniocaudal (CC) mammogram shows a large ill-defined focal asymmetry. (C) Ultrasound showed an irregular taller than wide hypoechoic mass with posterior shadowing. Ultrasound-guided core biopsy performed which showed fat necrosis. (D) A 51-year-old woman with history of left breast cancer, status post lumpectomy and radiation therapy. Routine mammogram showed a new ill-defined asymmetry in the posterior depth left upper breast (arrow). (E) Ultrasound showed a solid ill-defined hypoechoic mass with an echogenic peripheral halo. Ultrasound core biopsy showed fat necrosis.