Unusual Nonrefractile Eosinophilic Crystal in Breast Ducts in a Patient with Invasive Mucinous Carcinoma

A 72-year-old, G4P2 white woman presented with a recent abnormal mammogram showing a nodule at 8 o'clock of her right breast and indeterminate calcification in the subareolar region. An initial stereotactic core followed by wide local excision and sentinel node biopsy showed a pT1aN0(sn)M(na) low-grade invasive mucinous carcinoma. In dilated benign ducts, adjacent to the carcinoma, numerous eosinophilic, nonrefractile crystals were identified.