Primary Breast Involvement in Erdheim-Chester Disease: A Rare Presentation.

Erdheim-Chester disease (ECD) is a rare multisystem histiocytic neoplasm. Breast manifestations of this condition are exceedingly rare with fewer than 20 cases reported in the literature. We present a case report of a 40-year-old female patient with a 5-year history of breast enlargement and pigmentation who was diagnosed with ECD involving the bones, retroperitoneum and breast, highlighting key imaging and pathologic features that led to the diagnosis. ECD should be considered in the differential diagnosis of infiltrative breast disease. Considering this differential diagnosis allows appropriate further assessment and management.