The sinonasal undifferentiated carcinoma (SNUC) is an aggressive and rare n
eoplasm arising in the nasal cavity and the paranasal sinuses. To date, ove
r 50 cases of histologically proven SNUCs have been reported since its orig
inal description in 1986. Presenting symptoms include facial pain, nasal ob
struction, diplopia, epistaxis, proptosis, and periorbital swelling. The hi
stologic features of this neoplasm include cohesive cells arranged in nests
, ribbons, and trabeculae. The cells exhibit hyperchromatic nuclei and a hi
gh nuclear to cytoplasmic ratio. A brisk mitotic rate, tumor necrosis, and
vascular invasion are prominent features. Confirming the diagnosis of SNUG
at the light microscopic level can be challenging, since the microscopic di
fferential diagnosis includes olfactory neuroblastoma, rhabdomyosarcoma, un
differentiated nasopharyngeal carcinoma (lymphoepithelioma), malignant lymp
homa, malignant melanoma, and neuroendocrine (small. cell undifferentiated;
oat cell) carcinoma. Sinonasal undifferentiated carcinoma can be different
iated from these other neoplasms by correlating clinical, light microscopic
, histochemical, immunohistochemical, and ultrastructural characteristics.
Aggressive, multimodal therapy can provide the best opportunity for local c
ontrol of this neoplastic process, but the optimal treatment has yet to be
determined.