E1495. Adenomyoepithelioma of the Breast: An Imaging Review
  1. Katherine Smith; Mayo Clinic
  2. Tara Anderson; Mayo Clinic
  3. Lyndsay Viers; Mayo Clinic
  4. Robert Maxwell; Mayo Clinic Florida
  5. Bhavika Patel; Mayo Clinic Arizona
  6. Malvika Solanki; Mayo Clinic
  7. Katrina Glazebrook; Mayo Clinic
Adenomyoepithelioma (AME) of the breast is a rare tumor, thus far only described in case reports and small case series. AME is usually benign, but malignant degeneration has been reported. AME is characterized by dual differentiation into luminal and myoepithelial cells. The rarity of this neoplasm coupled with its varying architecture can sometimes lead to a false positive diagnosis of carcinoma. The recommended treatment strategy is surgical excision due to a propensity for local recurrence. The imaging features of this entity have not yet been well documented. Previous literature has described the mammographic appearance as an irregular mass with indistinct margins or architectural distortion without suspicious microcalcifications. Similarly, the sonographic appearance has been described as concerning for malignancy, with irregular shape, non-circumscribed margins, and acoustic shadowing.

Educational Goals / Teaching Points
We aim to further describe the imaging appearance of AME based on a series of cases at our institution following IRB approval. We identified 13 cases of AME using a retrospective search of imaging and pathologic databases – 12 benign and 1 malignant, with 2 of the benign cases demonstrating features of atypia.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
All of the patients were female with a mean age of 57 years (range 41-77 years). Initial presentation was: screening mammogram (5), palpable breast mass (4), diagnostic mammogram with an unrelated complaint (1), and not available in the medical record (4). Mammographic appearance (n=13) is as follows: focal asymmetry (3), mass with obscured margins (4), mass with circumscribed margins (3), mass with spiculated margins (1). None of the cases contained calcifications. Sonographic appearance (n=11) is as follows: irregular hypoechoic mass (7), complex cystic mass (3), and solid, well circumscribed mass (1). Two cases had documented internal vascular flow and one case was explicitly negative for internal Doppler flow. Two cases were evaluated with MRI. One case was a well-circumscribed, enhancing mass with an area of high signal intensity on T1 without T2 hyperintensity, whereas the other was characterized by non-mass enhancement with washout kinetics. Treatment was as follows: complete excision (8), conservative management with observation (3), unknown (1), and mastectomy with axillary node dissection (1, malignant AME case). Mean follow-up interval was 24 months (range 1-68 months). One case treated with complete excision resulted in a recurrence at 28 months. Four cases were lost to follow-up.

AME of the breast is an uncommon tumor that can be mistaken for a carcinoma on imaging or pathologically. In our series, mammographic findings include focal asymmetry or a mass with circumscribed or obscured margins. Although the literature reports architectural distortion as a frequent mammographic finding, this feature was only seen in one of our patients. Sonographic findings included an irregular hypoechoic mass or a complex cystic mass. On MRI it may present as non-mass enhancement or an irregular mass.