Two Breasts, Two Malignancies: Discordant Bilateral Breast Cancers With Brain and Bone Metastases

Synchronous bilateral breast cancers (BBCs) with discordant histology are rare and present unique diagnostic and therapeutic challenges, particularly in the setting of metastatic disease.We report a case of synchronous BBCs with discordant histology in the setting of brain, pulmonary, and osseous metastases, underscoring the importance of comprehensive bilateral evaluation and individualized management strategies.A 59-year-old female patient presented with an enlarging, painful exophytic mass on the left chest wall with a past medical history significant for untreated (Grade 3, ER+/PR-/HER2-) invasive ductal carcinoma (IDC) of the left breast two years earlier.During the current admission, imaging studies and assessments demonstrated invasive lobular carcinoma (ILC; ER+/PR-/HER2 IHC 2+) on the right breast with a right cerebellar mass, significant edema and mass effect, nodules in the middle lobe of the right lung, and an abnormal bone scan.Multidisciplinary consultation was obtained from breast surgery, radiation oncology, and neurosurgery; however, the patient declined surgical intervention and palliative radiation therapy and elected hospice care.