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Breast Imaging

E2794. Occult Breast Cancer Presenting as Axillary Nodal Metastasis: What the Radiologist Needs to Know

Etesami M,  Sheiman L,  Levesque P. Yale University School of Medicine, New Haven, CT

Address correspondence to L. Sheiman (laura.sheiman@yale.edu)

Background Information: Occult breast cancer (OBC) presenting as axillary nodal metastasis is an uncommon presentation of breast cancer that is defined as axillary lymph node metastasis without clinical, mammographic, or sonographic evidence of a primary breast cancer. Abnormal axillary lymph nodes may be detected by clinical examination or imaging, resulting in a biopsy. The radiologist may be the first to encounter this challenging scenario and direct imaging evaluation. We present an algorithm-based approach to the diagnostic workup of suspected OBC as well as a review of the management options.

Educational Goals/Teaching Points: The goal of this exhibit is to review the definition of OBC presenting as axillary nodal metastasis and present an algorithm-based approach to the diagnostic workup of suspected OBC with case examples. Cases will be presented with clinical history and imaging findings on mammography with digital breast tomosynthesis, ultrasound, MRI, and PET/CT. Reasons why the primary cancer was not initially detected on retrospective review of cases initially thought to represent a primary OBC will also be addressed. Surgical and nonsurgical management options of OBC and their outcomes will be discussed.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Initial presentation of an abnormal axillary lymph node may be detected on mammogram, ultrasound, other radiographic studies, or physical examination. Biopsy of the abnormal axillary lymph node can generally be performed under ultrasound guidance. Pathologic testing for immunohistochemical markers including estrogen and progesterone receptors and HER2 is recommended to help confirm breast lesion origin. Breast MRI with contrast should be included in the workup of patients with suspected OBC regardless of breast density. MRI may reveal a suspicious finding prompting MR-guided biopsy or second-look evaluation with ultrasound. Although traditionally patients with OBC underwent axillary lymph node dissection (ALND) with mastectomy, current evidence suggests that axillary lymph node dissection with whole breast radiation therapy is similar to ALND with mastectomy for mortality, locoregional recurrence, and distant metastasis rates. Chemotherapy and endocrine therapy may also be included in the treatment of OBC.

Conclusion: OBC presenting as axillary nodal metastasis can be a challenging diagnosis; however, the radiologist can help direct appropriate imaging workup with ultrasound, MRI, CT, and PET/CT. Image-guided biopsies will help elucidate the diagnosis. Management strategies of OBC are evolving with ALND and whole breast radiation therapy considered to be equivalent to ALND and mastectomy.