Pulmonary leiomyosarcoma metastatic to the thyroid gland: Case report and review of the literature

Background: Leiomyosarcoma metastatic to the thyroid is extremely rare. Especially, metastasis of pulmonary leiomyosarcoma to the thyroid is extremely rare-only one such case has been previously reported. Case presentation: A 55-year-old woman presented with a chief complaint of a cough of 1.5 months duration. Chest radiography (PA view) and chest computed tomography revealed 1 cm sized subpleural nodule in left apical lung and a 8.3. ×. 4 cm sized, lobulated mass in anterior segment of left upper lobe of the lung. We decided on left upper lobectomy and excision by video-assisted thoracoscopic surgery (VATS). They were leiomyosarcomas. During follow-up chest computed tomography at 23 months after first surgery, we noticed that a nodule on the left lobe of the thyroid gland had increased in size over 3 months. The patient underwent total thyroidectomy and central lymph node dissection. Immunohistochemical staining showed that tumor cells were positive for smooth muscle actin, focal positive for desmin and positive for vimentin, but negative for CD34 and S-100 protein. C-kit staining showed focal, weak positivity. The Ki-67 proliferation index was around 30-40%. Conclusions: Our case represents the first report of pulmonary leiomyosarcoma metastatic to the thyroid, although extrapulmonary leiomyosarcomas metastatic to the thyroid is encountered infrequently.