Pitfalls in microscopic diagnosis of undifferentiated carcinoma of nasopharyngeal type (lymphoepithelioma).

Isolated cervical lymph node metastases from undifferentiated carcinoma of nasopharyngeal type (UCNT) or lymphoepithelioma (LE) pathologically may be mistaken for malignant lymphomas. The case histories of four patients in whom metastatic UCNT in lymph nodes pathologically simulated Hodgkin's disease (HD) and other non epithelial malignancies are reported. Initial lymph node biopsies showed a cellular and architectural context suggestive of HD in three cases. "Lacunar" cells were seen associated with fibrosis and numerous eosinophils in Case 1; cells indistinguishable from diagnostic Reed-Sternberg cells were recognized in Case 4. Case 3 showed some additional features suggestive of malignant histiocytosis. Subsequent biopsies revealed a primary UCNT of the nasopharynx (Case 1) and typical UCNT lymph node metastases (Cases 3 and 4). In Case 2, an immunoblastic lymphoma and a spindle cell sarcoma, respectively, were mimicked by consecutive lymph node metastases. A primary UCNT of palatine tonsil was found five years later. This report emphasizes that deceptive features of metastatic UCNT in lymph nodes may produce serious difficulties in the correct recognition of the tumor on pure histologic grounds. In order to minimize the possibility of misdiagnosis, additional cytochemical, immunohistochemical and serologic studies should be considered, especially when a young patient presents with spinal or infraclavicular lymphadenopathies and no lesion is evident in the nasopharynx.