Nasopharyngeal Type Undifferentiated Carcinoma

ICD-O:8082/3

Although nasopharyngeal carcinoma (NPC), also known as lymphoepithelioma, almost invariably arises in the nasopharynx, "bona fide" primary sinonasal na-sopharyngeal-type undifferentiated carcinomas (PSN-PC) have recently been reported [127]. Due to the un-differentiated appearance of cells in NPC and PSNPC, these tumours may be lumped together with SNUC if unaware of their differences [48, 80, 127]. SNUC does not arise in the nasopharynx, but bulky lesions may extend into this region. Also, NPC may extend from the nasopharynx into the sinonasal region. The distinction between these tumours can generally be made on purely histological grounds, since SNUC lacks the lymphoplasmacytic cell infiltrate seen in most cases of NPC and PSNPC. Immunohistochemistry and in

Table 2.2. Sinonasal undifferentiated tumors. Immunohistochemistry and genetics.

Ampl

CK NSE S-100 CG SYN NF EBV L MIC-2 t11;22 N-myc

SNUC sinonasal undifferentiated carcinoma, SCC small cell (neuroendocrine) carcinoma, PSNPC primary sinonasal nasopharyngeal-type carcinoma, SNML sinonasal malignant lymphoma, PNET primitive neuroectodermal tumour, ONB olfactory neuroblastoma, MNB metastatic neuroblastoma, CK cytokeratin, NSE neuronal specific enolase, S-100 Protein S-100, CG chromogranin, SYN synap-tophysin, NF neurofilaments, EBV Epstein-Barr virus, L lymphoma markers, MIC-2 CD99, t(11;22) EWS-FLI1, Ampl amplification, (+) positive only in sustentacular cells situ hybridisation are of great help in difficult cases. All three, NPC, PSNPC, and SNUC, react positively for low molecular weight cytokeratins and EMA. In contrast, NPC and PSNPC are positive for EBV, whereas SNUC is negative. Until very recently, confusion of NPC and PSNPC with SNUC has led to the belief that some SNUC were related to EBV. The sharp distinction of these entities is crucial because NPC and PSNPC have a better prognosis and are more responsive to radiation therapy than SNUC.

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