Review of Nonmammary Metastases to the Breast: Imaging and Clinical Presentation

Objectives: The purpose of our study is to review the imaging findings of breast metastases from nonmammary sources at our institution and to explore the mode of initial detection of these breast metastases. Methods: In this study, we reviewed our electronic medical record and our breast imaging database for all patients who presented with nonmammary metastases to breasts between 5/1/2009 and 12/1/2019. We reviewed all available imaging data, clinical notes, and pathology reports. Results: Sixteen cases of nonmammary metastases to the breast were included in this study, of which there were 4 (25%) metastases from melanoma, 3 (19%) from carcinoid tumor, 2 (13%) from lung cancer, 2 (13%) from leiomyosarcoma, 1 (6%) each from lipsarcoma, renal cell carcinoma, colon cancer, neuroendocrine tumor, and adenoid cystic carcinoma. 6/8 (75%) lesions that had breast imaging were oval in shape with circumscribed or microlobulated margins on mammography and/or ultrasound. 13/16 (81%) breast metastases were asymptomatic and diagnosed on systemic staging exams. Three out of 16 (19%) nonmammary breast metastases were palpable and were diagnosed on subsequent breast imaging. Conclusions: Most (25%) nonmammary breast metastases in our patient population occur from melanoma and most breast metastases (75%) are oval in shape with circumscribed or microlobulated margins. Majority (81%) of these lesions are asymptomatic and initially diagnosed on systemic staging tests, and the remaining are discovered as palpable lesions.