Septic Pulmonary Embolism due to Methicillin-Resistant Staphylococcus aureus Bacteremia during Adjuvant Chemotherapy for Breast Cancer: A Case Report

Introduction: Septic pulmonary embolism (SPE) is a rare but serious complication in patients with cancer and is often difficult to distinguish from pulmonary metastases. Case Presentation: A woman in her 50s with a history of atopic dermatitis underwent left mastectomy and sentinel lymph node biopsy for hormone receptor-positive, HER2-negative breast cancer, followed by weekly adjuvant paclitaxel chemotherapy. After the seventh cycle, fever and left-sided neck pain developed. Physical examination revealed scalp folliculitis. Laboratory tests showed leukopenia and elevated C-reactive protein levels. Chest computed tomography (CT) demonstrated multiple subpleural nodules, initially suggestive of breast cancer metastasis; however, blood cultures obtained on admission yielded gram-positive cocci on the same day. Empirical intravenous antibiotic therapy was initiated and later deescalated to oral tedizolid after methicillin-resistant Staphylococcus aureus was confirmed. Fever resolved by day 5, and follow-up CT scans showed improvement with continued antibiotic therapy. Conclusion: SPE should be considered in patients with breast cancer who develop fever and new pulmonary nodules during adjuvant chemotherapy, particularly in those with underlying skin conditions or chemotherapy-induced immunosuppression. Prompt recognition and targeted antibiotic therapy are essential for achieving favorable clinical outcomes.