A rare case of undifferentiated nonkeratinizing carcinoma of the lip mucosa.

Undifferentiated nonkeratinizing carcinoma (UNC) is a poorly differentiated squamous cell carcinoma accompanied by a prominent reactive lymphoplasmacytic infiltrate that can occur in many anatomic sites. It shares morphologic features with undifferentiated nonkeratinizing nasopharyngeal carcinoma, in which a strong association with Epstein-Barr virus (EBV) has been noted. Among UNCs arising outside the nasopharynx, the linkage with EBV is variable; in particular, the few cases of UNC of the lip described thus far have been negative for EBV.