Occult pleomorphic lobular breast carcinoma presenting exclusively as microangiopathic hemolytic anemia and circulating tumor cells: An autopsy case report

Occult breast cancer (OBC) presents most commonly as solid tumor metastases when there is no clinically detectable primary breast lesion. We encountered a rare case of OBC in a 56-year-old woman mainly manifesting as cancer-related microangiopathic hemolytic anemia (CR-MAHA). She died suddenly during hospitalization and an autopsy was performed. Macroscopically, no primary tumor was identified. Microscopically, a massive number of circulating tumor cells (CTCs) were observed in almost all biopsied organs. The morphology and the immunohistochemical profile were consistent with pleomorphic lobular carcinoma (PLC) of the breast. Therefore, this is a rare case of OBC presenting exclusively in the form of CTCs originating from PLC. Awareness of this rare clinical presentation can aid in the correct diagnosis and appropriate patient management in the future.