Abstract
BACKGROUND: Pulmonary tumor thrombotic microangiopathy (PTTM), a rare complication of advanced cancer, is histologically characterized by tumor embolisms and fibrocellular intimal proliferation of small pulmonary arteries and arterioles. PTTM usually has an extremely poor prognosis, and antemortem diagnosis is very difficult. CASE PRESENTATION: A 65-year-old woman with a 5-year history of clinical stage IIA (T2N0M0) invasive ductal carcinoma of the left breast was hospitalized for worsening shortness of breath, hemoptysis, and cough since 2 months. She had previously received neoadjuvant chemotherapy and left mastectomy. Because the cancer cells were positive for human epidermal growth factor receptor 2 (HER2), four cycles of trastuzumab had been administered as adjuvant chemotherapy. On admission, chest computed tomography (CT) showed peripheral consolidations in both the lower lobes and a mediastinal mass. Specimens obtained on video-assisted thoracoscopic surgical biopsy revealed tumor cell embolism, intimal fibrocellular proliferation of small arteries, fibrin thrombi, recanalization, and infarction in the left lower lobe, as well as metastasis to the mediastinal pleura. Immunohistochemical staining of the tumor cells revealed positivity for HER2, and a diagnosis of recurrent breast cancer with PTTM was made. Four cycles of trastuzumab resulted in rapid improvement of her symptoms and CT findings of peripheral consolidations and the mediastinal mass. CONCLUSION: An antemortem diagnosis of PTTM was made in a patient with HER2-positive recurrent breast cancer. Trastuzumab was effective for not only breast cancer but also PTTM.