Amyloid in the Breast: Retrospective Review with Clinic‐Pathologic and Radiologic Correlation of 32 Cases from a Single Institution

AIMS Mammary amyloid is an uncommon and easily overlooked pathologic diagnosis with ambivalent presentation. Herein, we delineate the clinicopathologic and radiographic characteristics of mammary amyloid. METHODS AND RESULTS The Department of Pathology database was searched from 1993 through 2019 for keywords "breast" and "amyloid", yielding 32 cases from 23 patients, including consultation cases. All patients were female with age range 52-81 (mean 67.4 years). The left breast was involved more than the right (43% vs. 33%, respectively); bilateral amyloid involvement was also present (24%). Amyloid was most often associated with a benign histopathologic diagnoses (57%), lymphoma in 39% (all B-cell lymphomas, 5 of 9 were MALT lymphoma) and rarely with a concurrent epithelial malignancy (invasive lobular carcinoma, 4%). Of the 14 patients with available clinical history, amyloid presented as a mass clinically or radiographically (6 patients, 43%), as microcalcifications (5 patients, 36%), and only occasionally as an asymmetry (14%) or fibroglandular density (7%). Microscopic examination detected microcalcifications in an additional 9 cases (total 14 patients, 44% of the cohort). Interestingly, one patient had concurrent epithelial and hematologic malignancy, and amyloid within an axillary lymph node. Comorbidities included autoimmune diseases and multiple myeloma. CONCLUSION The majority of mammary amyloid cases are associated with benign histopathologic findings while imaging most frequently noted microcalcifications or mass lesions. To avoid overlooking amyloid as simply fat necrosis or fibroelastotic stromal change, a low threshold for performing ancillary stains should be considered in elderly women with benign core needle findings performed for mass lesions or microcalcifications.