Treatment of Leptomeningeal Carcinomatosis Following Treatment of Cerebellar Metastasis of HER2+ (Human Epidermal Growth Factor Receptor 2 Positive) Breast Cancer: Case Report and Review of Literature.

Leptomeningeal carcinomatosis (LC) after metastasis of breast cancer is a rare occurrence with potentially devastating complications. Treatment options are limited, and there is a lack of literature on this topic. We report the case of a 38-year-old woman with estrogen/progesterone receptor negative (ER/PR-), human epidermal growth factor receptor 2 positive (HER2+) invasive ductal carcinoma of the left breast who underwent bilateral mastectomies with axillary lymph node dissection and chemotherapy treatment. The patient returned 11 months later with persistent headaches. Imaging and resection found cerebellar metastasis of the breast carcinoma. The brain metastasis was treated with further chemotherapy and stereotactic radiosurgery. Follow-up imaging showed the development of small lesions outside the radiation site. Metabolic studies were performed to determine if the new lesions were due to tumor recurrence or radiation necrosis, but the studies were inconclusive as to the etiology of these lesions. The patient later developed LC that was successfully treated with full resolution of the disease using intrathecal trastuzumab. There are currently no consensuses on treatment guidelines for treating LC. Here, we demonstrate successful treatment of LC from an ER/PR-, HER2+ breast carcinoma with intrathecal trastuzumab.