**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Michael Keeney, Mayo Clinic, Rochester, MN

**Main Body of the Abstract**
Background: Breast amyloidosis is uncommon, and little is known about its clinicopathologic and proteomic features.
Aim: To evaluate the clinicopathologic and proteomic features of breast amyloidosis.
Material & Methods: The demographic and proteomic features of all Congo red-positive breast tissue specimens typed by a clinical proteomics-based amyloid typing assay (LC-MS/MS) in the Mayo Clinic reference laboratory between August 2008 and December 2023 (n = 36,864) were reviewed (n=450). Clinical information was available for 29 patients.
Results: Average age was 66.9 years with female:male ratio of 55:1. The vast majority (n=435, 97%) were immunoglobulin-associated and included AL-lambda (n=247, 57%), AL-kappa (n=168, 39%), and AH (n=20, 5%). Other amyloid types included AA (n=7; 2%), ATTR (n=4, 1%), AIns (n=1), AFuz (n=1), AGel (n=1) and ALac (n=1). We detected amino acid abnormalities indicative of known amyloidogenic mutations (V122I and L107V) in 2 ATTR cases (2/4, 50%). 11/19 (58%) AL patients who had monoclonal protein studies performed had an M-spike. Of the 9 patients with an M-spike for whom cardiac information was available, 8 (89%) had no cardiac involvement and the remaining case was equivocal. 27/29 (93%) were alive at last follow-up (median=4.9 months, range=2.1 to 170.1 months).
Summary & Conclusion: Breast amyloidosis typically occurs in older women. The vast majority are  immunoglobulin-associated, but other types can occur in this site. Although the presence of an associated M-spike is common, associated systemic amyloidosis is rare. These findings suggest that breast amyloidosis is usually immunoglobulin-associated and is commonly a localized phenomenon.



Clinicopathologic and Proteomic Features of Breast Amyloidosis PC89 (#556)

We invite you to attend the XIX International Symposium on Amyloidosis to be held in Rochester, MN.

This symposium is organized as a hybrid meeting (with the focus on in-person) held from Sunday, May 26 through Thursday, May 30, 2024.

Together with the ISA Board and members of Mayo Clinic, a very attractive scientific hybrid program is being planned. The program will cover a variety of types of systemic amyloidosis: ATTR (hereditary and wild-type), AL (light-chain), AA and less frequent forms. There will be key lectures, specific symposia including those company sponsored, oral presentations and poster sessions of accepted abstracts.

COURSE DESCRIPTION
This program will provide a comprehensive review of state-of-the-art education in systemic amyloidosis: basic science, pathophysiology, diagnosis, current and emerging treatments. Scientific presentations will include competitive oral and poster abstracts. The rapid evolution of scientific discovery and expanding treatment options has created tremendous interest in the field and this meeting will fill and important gap in educating scientists and clinicians.