Primary pulmonary small leiomyosarcoma arising from bronchial smooth muscles

A 74-year-old woman was admitted in an hospital because of abnormal lung shadow in chest X–P. Imaging modalities including CT, MRI, and PET demonstrated a small (12 mm in diameter) mass in the periphery of the right upper lobe. Although biopsy and cytology were negative, wedge resection was performed. Grossly, the lesion was a round white tumor measuring 10 × 10 × 9 mm located beneath the pleura. Microscopically, the tumor consisted of proliferation of atypical spindle cells with hyperchromatic nuclei. The tumor cells were continuous with bronchial smooth muscle. Mitotic figures were recognized in 20 per 10 high power fields. There were foci of necrosis and deposition of dusts and hemosiderin. Residual bronchi were present within the tumor. Immunohistochemically, the tumor cells were positive for vimentin, α-smooth muscle actin, caldesmon, and Ki-67 (labeling = 50%), but negative for cytokeratins (AE1/3, CAM5.2, KL-1, and polyclonal wide), cytokeratin 5/6, cytokeratin 7, cytokeratin 20, epithelial membrane antigen, melanosome, TTF-1, desmin, CD34, calreninin, D2-40 (podoplanin), S100 protein, p53 protein, myoglobin, KIT, and platelet-derived growth factor receptor-α (PDGFRA). The author diagnosed the lesion as leiomyosarcoma. After the pathological diagnosis, CT, MRI and PET of the whole body were performed, but did not reveal any tumors including the uterus. The patient was followed up, and three years later a recurrent lesion (20 mm in diameter) was identified in the right upper lobe near the previous tumor. Biopsy showed leiomyosarcoma with histology and immunohistochemical findings similar to the previous tumor. Further operation was impossible because of her medical conditions. She was treated by chemotherapy and followed up. She was now alive with the small pulmonary tumor, which shows no rapid growth.