[Clinicopathological study of Ewing's sarcoma/primitive neuroectodermal tumor in oral and maxillofacial region].

OBJECTIVE: To study the clinicopathological features and diagnostic criteria of Ewing's sarcoma/primitive neuroectodermal tumor (Ewing's sarcoma/PNET) in oral and maxillofacial region. METHODS: There were 15 patients with Ewing's sarcoma/PNET in the last 35 years at our hospital, aged 1-49 years and mean 14.5 years. The most common manifestation was swelling of the affected region. The cases were analyzed and histological and immunohistochemical studies were also conducted to examine CD99 (12E7), Vimentin, NSE, S-100, Syn, CD45 (LCA), desmin. RESULTS: (1) The most common histological pattern of Ewing's sarcoma/PNET was a lobular arrangement of uniform, small, hyperchromatic cells in a fibrous background. Some of these tumors were rich in cytoplasmic glycogen. (2) Of the 7 cases, IHC was positive for CD99 (12E7) and Vimentin and negative for lymphoid (CD45), muscle (desmin) markers. S-100 was positive in 4 cases and NSE negative in 3, Syn positive in 1. NSE, S-100, Syn were all negative in 2 cases. CONCLUSIONS: Ewing's sarcoma/PNET is more common in teenagers and young people. Immunohistochemistry is essential to distinguish Ewing's sarcoma/PNET from other small round cell tumors. Immunohistochemistry is useful in the diagnosis.