Leptomeningeal carcinomatosis from breast cancer initially mimicking cerebral infarction on MRI.

A female patient in her early 50s with breast cancer underwent breast-conserving surgery, followed by radiation therapy. She developed multiple lung and bone metastases and was started on chemotherapy with bevacizumab and paclitaxel 3 years later. After 6 months of chemotherapy, she developed a decline in conversation and memory. Magnetic resonance imaging (MRI) was conducted and showed multiple cortical and subcortical lesions and nodules with restricted diffusion but with no contrast enhancement on gadolinium (Gd) enhanced T1-weighted image, raising a suspicion of Trousseau's syndrome. A follow-up MRI revealed unchanged signal intensity of the lesions but with minimal enlargement. The cerebrospinal fluid cytology was negative for malignancy. Consequently, an open biopsy of the cortical lesion was conducted. Histopathology showed that the tumor cells were morphologically similar to the primary breast cancer extending from the brain surface along the Virchow-Robin spaces, which yielded a diagnosis of leptomeningeal carcinomatosis from breast cancer. Contrast enhancement on Gd-MRI may be impaired in case of tumor spread along the perivascular space or in patients treated with bevacizumab.