Breast cancer: an atypical and challenging presentation

Introduction: Paraneoplastic syndromes are rare manifestations of oncological diseases, posing a diagnostic challenge.Case report: We report the case of a young female patient hospitalized with a neurological condition clinically compatible with stiff-person syndrome (SPS), presenting with an inability to walk independently at admission.During hospitalization, a diagnostic workup revealed an invasive carcinoma of no special type (NST), luminal B, with clinical staging cT1c N1 Mx, in the left breast.The diagnosis of paraneoplastic SPS with positive anti-amphiphysin antibodies was established.The patient underwent neoadjuvant chemotherapy with anthracyclines and taxanes, followed by left subcutaneous mastectomy and axillary lymph node dissection.Histology revealed residual invasive disease (NST): ypT1c N1a.Of the proposed adjuvant treatment, she has completed radiotherapy and continues with hormonal therapy and bisphosphonates.Conclusion: With the oncological treatment, the neurological symptoms improved progressively and significantly, allowing discontinuation of symptomatic treatment.Nine months post-surgery, she is pain-free, spasm-free, and has regained full autonomy.