Opsoclonus-myoclonus Syndrome in a Female Breast Cancer Patient: A Case Report and Literature Review.

Background/aim: Opsoclonus-myoclonus syndrome (OMS) is rarely associated with breast cancer. This paraneoplastic syndrome poses significant diagnostic and therapeutic challenges for physicians.

Case report: This article discusses a case of a 58-year-old Caucasian woman with complex neurological symptoms identified as paraneoplastic OMS due to non-metastatic breast carcinoma. This autoimmune disorder is associated with onco-neural autoantibodies, precisely type II anti-Ri nuclear antibody (ANNA-2), which targets the intracellular Ri antigen (Ri-PNS) and cross-reacts with two neuron-specific antigens. A multidisciplinary approach involving neurologists played a crucial role in case management. Left breast biopsy revealed a poorly differentiated ductal infiltrating carcinoma of the left breast, with 95% positive estrogen receptors, 12% positive progesterone receptors, HER-2 1+, FISH not amplified, and Ki67 at 50%. The patient underwent quadrant surgery for breast cancer and received hormonal therapy with anastrozole. To date, the patient is cancer-free; however, OMS persists. Neurological treatment did not yield significant or durable results. In conclusion, the medical literature on OMS in patients with breast cancer is fragmentary.

Conclusion: This report illustrates the complexity of managing breast cancer patients with OMS and reinforces the critical need for a multidisciplinary approach.