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Cavernous sinus

16%

Cerebrum, meninges, cisterns

4%

Infratemporal fossa

9%

Orbit, orbital fissure(s)

4%

Hypopharynx

2%

Fig. 2.4 Positron emission tomography coupled with computed tomography (PET-CT) of nasopharyngeal carcinoma. Physical examination and biochemistry did not show any sign suggestive of distant metastases. X-ray chest was normal. PET-CT revealed multiple distant metastases in lung, liver and spleen, in addition to extensive local infiltration and bilateral cervical lymph nodes.

Fig. 2.4 Positron emission tomography coupled with computed tomography (PET-CT) of nasopharyngeal carcinoma. Physical examination and biochemistry did not show any sign suggestive of distant metastases. X-ray chest was normal. PET-CT revealed multiple distant metastases in lung, liver and spleen, in addition to extensive local infiltration and bilateral cervical lymph nodes.

Serological studies

Positive serology against Epstein-Barr virus (EBV) is found in close to 100% of patients with non-keratinizing NPC {976}. IgA against viral capsid antigen (VCA) and IgG/IgA against early antigens (EA) are the most extensively used diagnostic tool, with the reported detection rates for NPC varying from 69-93%. Newer antibody tests based on recombinant EBV antigens such as EBV nuclear antigens (EBNA), membrane antigen (MA), thymidine kinase (TK), DNA polymerase (DP), ribonucleotide reductase (RR), DNAase, and Z transactivator protein (Zta) have shown promise when used in combination {378,537}.

Another approach is to test for elevated levels of circulating EBV DNA or RNA (BamH1-W, EBERs or EBNA1) by quantitative PCR (Q-PCR) in the plasma or serum, with reported sensitivity in NPC up to 96% {35,1514,1549,2346}.

Relevant diagnostic procedures

All patients should have complete physical examination and endoscopic examination of the nasopharyngeal region. Biopsies are taken from the gross lesions. In the absence of a gross lesion, multiple biopsies should be taken from the lateral, superior and posterior walls of the nasopharynx for patients with high suspicion of NPC.

Macroscopy

The tumour can appear as a smooth bulge in the mucosa, a discrete raised nodule with or without surface ulceration, or a frankly infiltrative fungating mass. Sometimes no grossly visible lesion is seen.

Tumour spread and staging

Tumour spread

NPC is notorious for its highly malignant behaviour, with extensive loco-regional infiltration, early lymphatic spread, and disproportionately high incidence of haematogenous dissemination. Erosion of skull base and paranasal sinuses, intracranial spread (via eroded bone or basal foramina), infiltration of cranial nerves, and extension to more distant structures (infratemporal fossa, orbit, hypopharynx) occur as tumour invasion advances.

With the rich lymphatic plexus in the nasopharynx, lymphatic spread occurs early in the course of disease. In patients staged by MR, about 20% of patients have no enlarged nodes, and about half have retropharyngeal node involvement {2314}. The jugulo-digastric node is by far the most common palpable node at presentation, and involvement of the posterior cervical chain is more frequent than with other head and neck cancers. The strong association between the topographic level of lymphatic extension and the increased incidence of distant failure reflects that haematogenous dissemination occurs mainly via the draining of the lymphatic trunks at the lower end of the jugular chain into the great vessels. The most common sites of haematogenous deposits are, in descending order of frequency, bone, lung, liver, and distant nodes {2575}.

Staging

The current TNM staging system {947, 2418} is customized for NPC, as the natural

Fig. 2.5 The relative frequency of cranial nerve palsy due to nasopharyngeal carcinoma at the time of diagnosis. Source: 722 patients treated at the Pamela Youde Nethersole Eastern Hospital, Hong Kong, 1994-2001.

Fig. 2.7 Nasopharyngeal nonkeratinizing carcinoma. This example is accompanied by an abundant desmoplastic stroma.

Fig. 2.6 Nasopharyngeal nonkeratinizing carcinoma. Tumour islands are obvious in the lymphoid stroma.

Fig. 2.7 Nasopharyngeal nonkeratinizing carcinoma. This example is accompanied by an abundant desmoplastic stroma.

behaviour and therapeutic considerations of NPC are so uniquely different from other head and neck cancers. With accumulation of supporting data from different countries {448,490,1061, 1119,1444,1592,1966}, there is little doubt that the current staging system is superior to the past systems, both in terms of improved predictive accuracy and more balanced stage distribution.

Nonkeratinizing carcinoma

Histopathology

The biopsies vary in appearance from the presence of a frank tumour with surface ulceration to subtle involvement of the mucosa beneath an intact surface epithelium {2316,2318,2735}. The tumour comprises solid sheets, irregular islands, dyscohesive sheets and trabec-ulae of carcinoma intimately intermingled with variable numbers of lymphocytes and plasma cells. Subclassification into the undifferentiated and differentiated subtypes is optional, since their distinction is of no clinical or prognostic significance, and different areas of the same tumour or different biopsies taken at dif ferent time intervals from the same patient may exhibit features of one or the other subtype. When both subtypes are seen in a specimen, the tumour may be classified according to the prominent subtype, or as nonkeratinizing carcinoma with features of both subtypes. The undifferentiated subtype, which is more common, is characterized by syn-cytial-appearing large tumour cells with indistinct cell borders, round to oval vesicular nuclei, and large central nucle-oli. The cells often appear crowded or even overlapping. Sometimes, the nuclei

Fig. 2.8 Nasopharyngeal nonkeratinizing carcinoma. A This example of differentiated subtype is characterized by sheets of tumour separated by a dense infiltrate of lymphocytes and plasma cells. B Tumour island in a lymphoid cell-rich stroma. Some lymphocytes are also seen within the tumour. C This tumour shows an uncommon trabecular growth pattern.

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Fig. 2.8 Nasopharyngeal nonkeratinizing carcinoma. A This example of differentiated subtype is characterized by sheets of tumour separated by a dense infiltrate of lymphocytes and plasma cells. B Tumour island in a lymphoid cell-rich stroma. Some lymphocytes are also seen within the tumour. C This tumour shows an uncommon trabecular growth pattern.

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Fig. 2.9 Cytological spectrum of nasopharyngeal nonkeratinizing carcinoma, undifferentiated subtype. A The cells exhibit a syncytial quality, and possess vesicular nuclei, prominent nucleoli and amphophilic cytoplasm. B The syncytial-appearing cells have vesicular nuclei, distinct nucleoli and lightly eosinophilic cytoplasm. There are some intermingled lymphocytes. C Focally, there can be cells with more distinct cell borders and a moderate amount of eosinophilic cytoplasm.

Fig. 2.9 Cytological spectrum of nasopharyngeal nonkeratinizing carcinoma, undifferentiated subtype. A The cells exhibit a syncytial quality, and possess vesicular nuclei, prominent nucleoli and amphophilic cytoplasm. B The syncytial-appearing cells have vesicular nuclei, distinct nucleoli and lightly eosinophilic cytoplasm. There are some intermingled lymphocytes. C Focally, there can be cells with more distinct cell borders and a moderate amount of eosinophilic cytoplasm.

can be chromatin-rich rather than vesicular. The scant cytoplasm is either amphophilic or eosinophilic. There can be small foci of primitive squamous differentiation, where groups of tumour cells exhibit a slightly greater amount of lightly eosinophilic cytoplasm and slightly more distinct cell borders.

The differentiated subtype differs from the undifferentiated subtype in showing cellular stratification and pavementing, often with a plexiform growth, reminiscent of transitional cell carcinoma of the bladder {2317}. The tumour cells show fairly well-defined cell borders and sometimes vague intercellular bridges, and there may exceptionally be occasional keratinized cells. Compared with the undifferentiated subtype, the cells are often slightly smaller, the nuclear-cytoplasmic ratio is lower, the nuclei can be more chromatin-rich, and nucleoli are usually not as prominent.

A desmoplastic stroma is uncommon. Areas of coagulative necrosis are sometimes present, and can be extensive. The density of lymphocytes and plasma cells is highly variable. At one extreme, there are no or few lymphocytes within the tumour islands, although some lymphoid cells are present in between, which probably merely represent the native lym-phoid tissue in the nasopharyngeal mucosa. At the other extreme, abundant lymphocytes and plasma cells infiltrate the tumour islands, breaking them up into tiny clusters or single cells and obscuring the epithelial nature of the tumour; the term "lymphoepithelial carcinoma" may be applied for such cases. In metastatic sites, the lymphocyte density in the tumour may or may not be maintained. In some cases, scattered epithe-lioid granulomas are present, and may be so prominent as to mask the small islands of carcinoma {404}. Many admixed eosinophils are seen in about one-fourth of cases {830,1463,1555}. Some cases show a prominent infiltrate of neutrophils even in the absence of ulceration.

There are a number of inconstant features. The carcinoma cells can assume a plump or slender spindle shape focally or extensively, with formation of streaming fascicles. The nucleoli of the spindly cells are often not as prominent as the syncytial-appearing cells. In some cases, isolated or groups of tumour cells

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