[Clinicopathological Features of Intrathyroid Thymic Carcinoma]

Objective To investigate the clinicopathological features,immunohistochemical characteristics,diagnosis,treatment and prognosis of intrathyroid thymic carcinoma.Methods Clinical data of 7 patients with intrathyroid thymic carcinoma were retrospectively reviewed.Histological examination and immunohistochemical staining were performed on the surgically resected tumors.The infection of Epstein-Barr virus(EBV)was detected by EBER in situ hybridization.Results The 7 patients included 5 males and 2 females.The age ranged from 40 to 71 years,with a median of 54 years.The tumors were located in the thyroid gland,with the maximum diameter ranging from 2.2 cm to 6.0 cm and the average maximum diameter of(4.0±1.2)cm.All the patients underwent thyroid gland resection and local lymph node dissection.After operation,all the cases were treated with radiotherapy and five of them additionally received chemotherapy.Six patients were followed up for 10-163 months,all of whom were still alive,including 2 patients with recurrence in situ,1 patient with homolateral cervical lymph node metastasis and the rest with no recurrence or metastasis.CK-pan,P63,CD5 and CD117 were expressed in all the cases,while TTF-1,TG,CT and PAX8 were negative.One case of them expressed SYN and CgA.Ki-67 proliferation index ranged from 10% to 90%.EBER in situ hybridization showed negative results in all 7 cases.Conclusions Intrathyroid thymic carcinoma is a relatively low-grade malignant tumor.The combination of immunohistochemical CD5,CD117 and monoclonal PAX8 is helpful in the diagnosis and differential diagnosis of intrathyroid thymic carcinoma.EBV may not be involved in the development of intrathyroid thymic carcinoma.Thyroid gland resection plus central lymph node dissection is an important treatment measure for intrathyroid thymic carcinoma.For patients with regional lymph node metastasis and obvious peripheral tissue invasion,postoperative radiotherapy with/without chemotherapy can effectively delay the disease progression.