Pulmonary Lymphoepithelioma-like Carcinoma.

Pulmonary lymphoepithelioma-like carcinoma is a rare type of non-small cell lung cancer. The tumor is usually discovered in young, nonsmoking Asian populations. The patients are diagnosed at an earlier stage and have a better prognosis than those with other non-small cell lung cancers. Histologically, the tumor morphology is indistinguishable from undifferentiated carcinoma of the nasopharynx. It is characterized by nests or diffuse sheets of syncytial tumor cells, which show round to oval vesicular nuclei with prominent nucleoli, along with an admixed heavy lymphocytic and plasma cell infiltrate. The presence of Epstein-Barr virus in the tumor cells is crucial for the diagnosis. The differential diagnoses include lymphoepithelioma-like carcinoma from other sites and pulmonary involvement of lymphoma. EGFR mutations and ALK rearrangements are not commonly found in lymphoepithelioma-like carcinoma, in contrast to programmed death ligand-1 expression, which is shown in a majority of cases.