Lymphoepithelial carcinoma

Definition

Lymphoepithelial carcinoma is a poorly differentiated squamous cell carcinoma or histologically undifferentiated carcinoma accompanied by a prominent reactive lymphoplasmacytic infiltrate, morphologically similar to nasopharyngeal carcinoma.

ICD-O code 8082/3

Synonyms

Undifferentiated carcinoma; undifferentiated carcinoma with lymphocytic stroma; undifferentiated carcinoma of nasopharyngeal type; lymphoepithelioma-like carcinoma

Epidemiology

Sinonasal lymphoepithelial carcinoma is rare, and most reported cases have originated from Southeast Asia, where nasopharyngeal carcinoma is also prevalent {1216,1480,1558,2910}. It affects adults in the fifth to seventh decades, and there is a male predominance of approximately 3:1.

Etiology

Nearly all sinonasal lymphoepithelial carcinomas show a strong association with Epstein-Barr virus (EBV)

{801,1216,1480,1558,2910}.

Localization

Sinonasal lymphoepithelial carcinomas are more common in the nasal cavity than in the paranasal sinuses, although both sites may be involved simultaneously. The tumours may show local invasion of the palate, orbit, and base of skull.

Clinical features

Patients present with nasal obstruction, bloody nasal discharge or epistasis. Intracranial extension of tumour may cause proptosis and cranial nerve palsy {1216,1480}. There may be cervical lymph node and/or distant metastasis at presentation. Examination and biopsy of the nasopharynx is required to exclude loco-regional spread from a primary nasopharyngeal carcinoma.

Histopathology

The tumour infiltrates the mucosa in the form of irregular islands and sheets, usually without a desmoplastic stroma. The tumour cells possess relatively monotonous vesicular nuclei with prominent nucleoli. The cytoplasm is lightly eosinophilic, with indistinct cell borders, resulting in a syncytial appearance. The tumour cells may also appear plump spindly, with streaming of nuclei. Intraepithelial spread of tumour may sometimes be seen in the overlying epithelial lining. Necrosis and keratiniza-tion are usually not evident. The tumour is infiltrated by variable numbers of lymphocytes and plasma cells. In general, the inflammatory infiltrate is less promi nent than that seen in nasopharyngeal carcinoma. In some cases, the inflammatory cells may even be sparse {1216,1480}. The epithelial nature of the tumour can be confirmed by immunos-taining for pan-cytokeratin and epithelial membrane antigen. EBV encoded RNA (EBER) is strongly expressed by the tumour cells in most cases {801,1216,1480,1558,2910}.

Differential diagnosis

Sinonasal lymphoepithelial carcinoma must be distinguished from the vastly more aggressive sinonasal undifferentiat-ed carcinoma (SNUC). The presence of lymphoplasmacytic infiltrates, although helpful, cannot be relied on solely in making the distinction. SNUC is characterized by tumour cells with nuclear pleo-morphism, high mitotic rate and frequent necrosis. EBV status is also helpful since SNUC, except for rare cases from Asians, are EBV-negative {1216,1480, 1558}. Other important differential diagnoses are malignant melanoma and non-Hodgkin lymphoma.

Prognosis and predictive factors

The tumour responds favourably to local-regional radiotherapy even in the presence of cervical lymph node metastasis {623,1216,1480}. Distant metastasis (most often to bone), however, is associated with a poor prognosis.

Fig. 1.9 Primary lymphoepithelial carcinoma of the nasal cavity. A The intimate intermingling of the carcinoma cells with lymphoid cells imparts a lymphoma-like appearance. B Large carcinoma cells with indistinct cell borders, vesicular nuclei and prominent nucleoli are admixed with numerous small lymphocytes..

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