Lymphoepithelial carcinoma of the oral mucosa. A rare histopathologic subtype of squamous cell carcinoma

Abstract

<h3>Objectives</h3> Lymphoepithelial carcinoma (LEC) represents a rare histopathologic subtype of squamous cell carcinoma (SCC), which shares morphologic similarities with non-keratinizing undifferentiated nasopharyngeal carcinoma (NPC). LEC may be etiologically associated with EBV, especially in endemic regions. Although being described in several locations of the head and neck, the oral mucosa seems to be an infrequent site of involvement. Herein, we present a case of an EBV-negative oral LEC and discuss the diagnostic challenges. <h3>Findings</h3> A 51 year-old male Filipino patient suffering from chronic kidney disease presented for the evaluation of a swelling in the right mandible, first noticed by the patient a few days ago. Clinically, the right posterior mandibular gingiva appeared enlarged and hemorrhagic, covered by ulcerated mucosa, while the adjacent teeth displayed high mobility. Extraorally, a painful and slightly movable lymph node in the right submandibular area was palpated. Radiographic evaluation revealed extensive bone loss in the right posterior mandible. With a provisional diagnosis of lymphoma or SCC, an incisional biopsy was performed. Histopathologic examination revealed invasion of the underlying connective tissue by pleomorphic cells of epithelioid morphology, occasionally arranged in syncytial islands, arising from a partially ulcerated, non-keratinized squamous epithelium. A prominent diffuse lymphocytic cell infiltrate surrounding the tumor cells was also detected. The neoplastic cells expressed pancytokeratin, CK5/6, p63, and p40, while p16, LMP-1, and in situ hybridization for EBV RNA were negative. A final diagnosis of moderately to poorly differentiated SCC with features indicative of LEC was rendered and the patient was referred for further management. <h3>Conclusions</h3> LEC should be considered in the differential diagnosis of undifferentiated malignant neoplasms displaying close association with diffuse lymphoid aggregates. The evaluation of nasopharynx is justified to rule out metastatic NPC, as the separation of these two entities microscopically is not feasible.