Nasopharyngeal papillary adenocarcinoma and salivary glandtype carcinomas

Nasopharyngeal papillary adenocarcinoma

Definition

A low-grade adenocarcinoma characterized by an exophytic growth comprising papillary fronds and glandular structures.

ICD-O code

8260/3

Epidemiology

Nasopharyngeal papillary adenocarcinoma is extremely rare {1902,2672,2770}. The reported age range is 11-64 years (median 37 years) {1902,2672,2770}. Gender distribution is nearly equal {1902,2672,2770}.

Localization

The tumour most commonly involves the roof, lateral wall and posterior wall of the nasopharynx {2770}.

Clinical features

Nasal obstruction is the main presenting symptom. The diagnosis can be readily confirmed by endoscopic biopsy.

Macroscopy

The tumours are soft or gritty and exo-phytic, with a papillary, polypoid, or cauliflower appearance. The tumours measure up to 4 cm (median size 2.5 cm) {2770}.

Tumour spread and staging

The tumours usually remain confined within the nasopharynx except one reported case with extensive local invasion {1902}.

Histopathology

Nasopharyngeal papillary adenocarcinoma arises from the surface epithelium {2770}. The tumour comprises arborizing delicate papillary fronds and crowded glands. The lining columnar or pseudos-tratified cells have bland, round to oval nuclei and tiny nucleoli. Mitotic figures are rare; necrosis may be focally identified. Psammoma bodies may be found in some cases. The tumours are unencap-

sulated and infiltrate into the surrounding stroma.

Diastase-resistant, periodic acid-Schiff intracytoplasmic positive material is present; intraluminal and intracytoplas-mic mucicarmine staining may be focally identified. Immunohistochemical staining shows positive reactivity for epithelial markers (i.e., cytokeratin, epithelial membrane antigen), but there is no reactivity for thyroglobulin and S-100 protein. There is no association with Epstein-Barr virus.

Genetic susceptibility

A case has been reported in a patient with Turner syndrome {1902}.

Prognosis and predictive factors

This is an indolent low-grade malignant neoplasm with no metastatic potential. It has an excellent prognosis if a complete excision can be achieved {2770}.

Salivary gland-type carcinomas

These are very rare in the nasopharynx {2448}. Men are affected nearly three times more frequently than women {1389}. The age range is from 15-74 years with a median age of 50 years. The most frequent types are, in order of fre-

quency, adenoid cystic carcinoma, mucoepidermoid carcinoma and adeno-carcinoma not otherwise specified {2273}. Carcinomas at this site frequently present at an advanced stage and often with invasion of the base of the skull, intracranial extension and involvement of the cranial nerves.

Adenoid cystic carcinomas {336,1449,2273,2718} are typically insidious in onset, and symptoms may include middle ear effusion, epistaxis, diplopia and symptoms due to cranial nerve palsy (such as pain, paraesthesia, anaesthesia). The microscopic features are similar to those of adenoid cystic carcinoma elsewhere. The 5 and 10 year survival are 78% and 49.5% respectively, and 35% of patients will develop metastasis to bone or lung {2718}. Mucoepidermoid carcinomas {1321, 1389,2273} are microscopically similar to those in other sites but rarely psammoma bodies can be seen.

Other rare salivary gland-type carcinomas of the nasopharynx include epithe-lial-myoepithelial carcinoma {1174}, myoepithelial carcinoma {1899}, acinic cell carcinoma {1890} and polymorphous low-grade adenocarcinoma {1469,2763}.

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