Fig. 2.30 Nasopharyngeal follicular dendritic cell sarcoma/tumour. The atypical spindly cells are usually sprinkled with small lymphocytes (left). They are immunoreactive for CD21 (right).

immunophenotypically similar to those seen in the nasal cavity. Other types of NHL, for example, Burkitt lymphoma, follicular lymphoma, mantle cell lymphoma, extranodal marginal zone B-cell lymphoma of MALT type, and peripheral T-cell lymphoma unspecified may also affect the nasopharynx, but at a much lower frequency {420,1704,2849}. Please refer to the sections of 'non-Hodgkin lymphoma' in 'Tumours of the nasal cavity and paranasal sinuses' and 'Tumours of the oral cavity and oropharynx' for details.

Differential diagnosis

Distinction between nasopharyngeal carcinoma and DLBCL can be difficult at times because the carcinoma cells in nasopharyngeal carcinoma can appear discohesive due to submergence in a dense lymphoplasmacytic infiltrate, while DLBCL can sometimes form tight cell clusters. Positive immunostaining for cytokeratin would support the former diagnosis, and expression of lymphoid markers (including CD20) would support the latter. Infectious mononucleosis involving the nasopharynx can also mimic DLBCL {2547}, but can be suspected or recognized by the young age of the patient, presence of a range of large cells with apparent maturation to plasmablasts and plasma cells, lack of frank cytologic atypia, and polyclonal immunoglobulin staining in the large cells.

Extranodal NK/T cell lymphoma with small cell predominance can be difficult to recognize as being a malignant neoplasm. Histologic features suggestive of the diagnosis include extensive effacement of architecture, marked coagulative necrosis, angiocentric growth, and wide separation of the mucosal glands. The diagnosis is supported by the demonstration of sheets of CD56+, CD3e+, EBER+ cells. In the rare case of herpes simplex infection involving the nasopharynx, there can be a dense lymphoid infiltrate with extensive CD56 expression, causing confusion with extranodal NK/T cell lymphoma. In contrast to NK/T cell lymphoma, these CD56+ cells express CD4 and CD5, and there is no association with EBV. The diagnosis is confirmed by identifying the herpes simplex virus-infected multinucleated giant cells with ground glass nuclei with or without nuclear inclusions, which can be further confirmed by immunostaining for herpes simplex virus {2523}.

Prognosis and predictive factors

Radiotherapy is the treatment of choice for extranodal NK/T cell lymphoma , often in combination with additional treatment modalities {421}. Chemotherapy and/or radiotherapy is usually given for patients with DLBCL.

The overall survival rate for extranodal NK/T cell lymphoma of nasal-type is only 30-50% {421,422,1312,1838}. Factors associated with worse outcome include: advanced stage, poor performance status, B symptoms and bulky disease {422}. B-cell lymphomas show a slightly more favourable outcome {420}.

Follicular dendritic cell sarcoma / tumour

Follicular dendritic cell sarcoma/tumour is a rare tumour showing morphologic, immunophenotypic and ultrastructural features of follicular dendritic cells. Primary involvement of the nasopharynx is rare {189,359}, and may arise from an underlying hyaline-vascular Castleman disease {359}. Please refer to the section of 'Follicular dendritic cell sarcoma/tumour' in 'Tumours of the oral cavity and oropharynx' for details.

Extramedullary plasmacytoma

ICD-O code 9734/3

Approximately 22% of head and neck extramedullary plasmacytomas occur in the nasopharynx, which is the second most common site after the sinonasal tract. See corresponding section in 'Tumours of the nasal cavity and paranasal sinuses' for details.

Other haematolymphoid tumours

Castleman disease, extramedullary myeloid sarcoma and Rosai-Dorfman disease (sinus histiocytosis with massive lymphadenopathy) can occasionally affect the nasopharynx {359,2631,2637, 2760}. Please refer to Chapter 1 on 'Tumours of the nasal cavity and paranasal sinuses' for details.

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