Stage II HER2-Positive Breast Cancer With Anti-Yo Paraneoplastic Cerebellar Degeneration

What happened, in summary

A 53-year-old postmenopausal woman first sought emergency care for dizziness, ataxia, blurred vision and intermittent double vision. Brain imaging was initially normal. Four months later, while the neurologic symptoms continued, she noticed a new lump in her left breast. Biopsy showed high-grade invasive ductal carcinoma. She underwent a left simple mastectomy with sentinel lymph node biopsy. One of 3 nodes contained a 0.4 cm cancer deposit, while chest, abdominal and pelvic CT and a bone scan showed no distant metastases. Final pathology described a 2.6 cm grade 3 invasive ductal carcinoma that was estrogen-receptor negative, progesterone-receptor negative and HER2-positive. The breast cancer was Stage II. Her neurologic condition worsened, and anti-Yo antibodies confirmed paraneoplastic cerebellar degeneration. Two courses of IVIG produced no clinical improvement. Cancer treatment then included 4 cycles of doxorubicin and cyclophosphamide, followed by weekly paclitaxel with trastuzumab. The 12th paclitaxel cycle was held because of sensory neuropathy, while trastuzumab continued every 3 weeks for a 1-year course. Despite treatment and rehabilitation, the neurologic syndrome remained severely disabling. She became wheelchair-dependent, needed help with self-care and eventually moved to long-term care. Intensive rehabilitation produced moderate improvement in ataxia, but substantial functional impairment persisted.