Salivary neoplasms


Salivary neoplasms

INTRODUCTION

The wide range of different neoplasms that can affect the salivary glands has been classified by the World Health Organization (Box 49.1). The epithelial neoplasms, which are the most important, can be memorized by the mnemonic ‘A Most Acceptable Classification’ – most are benign but some are malignant (Tables 49.1 and 49.2):

BOX 49.1   WHO classification of salivary gland tumours

Malignant epithelial tumours

image Acinic cell carcinoma8550/3

image Mucoepidermoid carcinoma8430/3

image Adenoid cystic carcinoma8200/3

image Polymorphous low-grade adenocarcinoma8525/3

image Epithelial-myoepithelial carcinoma8562/3

image Clear cell carcinoma, not otherwise specified8310/3

image Basal cell adenocarcinoma8147/3

image Sebaceous carcinoma8410/3

image Sebaceous lymphadenocarcinoma8410/3

image Cystadenocarcinoma8440/3

image Low-grade cribriform cystadenocarcinoma

image Mucinous adenocarcinoma8480/3

image Oncocytic carcinoma8290/3

image Salivary duct carcinoma8500/3

image Adenocarcinoma, not otherwise specified8140/3

image Myoepithelial carcinoma8982/3

image Carcinoma ex pleomorphic adenoma8941/3

image Carcinosarcoma8980/3

image Metastasizing pleomorphic adenoma8940/1

image Squamous cell carcinoma8070/3

image Small cell carcinoma8041/3

image Large cell carcinoma8012/3

image Lymphoepithelial carcinoma8082/3

image Sialoblastoma8974/1

Secondary tumours

Morphology code of the International Classification of Diseases for Oncology (ICD-O) (821) and the Systematized Nomenclature of Medicine (snomed.org). Behaviour is coded /0 for benign tumours, /3 for malignant tumours and /1 for borderline or uncertain behaviour.

Table 49.1

The more common benign salivary gland epithelial neoplasms

Neoplasm Comment
Pleomorphic salivary adenoma (PSA) Most common
Warthin tumour Second most common benign neoplasm; associated with tobacco smoking; often multiple, sometimes bilateral; frequency increasing
Myoepithelioma Rare
Basal cell adenoma Older patients affected
Oncocytoma Older patients affected
May follow irradiation
May be bilateral
Canalicular adenoma Most common in upper lip, and in older patients

Table 49.2

The more common malignant salivary gland epithelial neoplasms

Neoplasm Comment
Carcinoma ex-PSA Variable prognosis
Acinic cell carcinoma Mainly in parotid
Poor prognosis
Mucoepidermoid carcinoma Most common malignancy
Adenoid cystic carcinoma Poor prognosis
Polymorphous low grade adenocarcinoma Most are seen in palate; good prognosis
Epithelial-myoepithelial carcinoma Most in major glands; variable prognosis

Most salivary gland neoplasms are epithelial, presenting as a unilateral swelling of the parotid and most are benign (Fig. 49.1). This can be remembered by the ‘rule of nines’ (an approximation) that states that 9 out of 10 salivary gland neoplasms:

The next most common neoplasm is carcinoma. Other neoplasms of major salivary glands are usually monomorphic adenomas (such as adenolymphomas), mucoepidermoid tumours or acinic cell tumours. Minor gland neoplasms are more often malignant (Fig. 49.1).

AETIOLOGY AND PATHOGENESIS

The aetiology is largely unknown, but associations have included:

image Tobacco smoking: at least in Warthin tumour.

image Infections such as:

image Occupation: rubber manufacturing, plumbing industry, woodworking, hairdressing, mineral exposure (nickel, chromium, cement, asbestos, silica)

image Ionizing radiation exposure, as in:

image Other radiation: concern about mobile telephones predisposing to epithelial parotid gland malignancy and mucoepidermoid carcinoma has not been resolved though they may almost double the risk of head tumours according to some studies.

image Genetics:

image genes expressed or altered in salivary neoplasms (Table 49.3) include particularly the PLAG1 (pleomorphic adenoma gene 1) on chromosome 8 and changes in 19p, particularly at 19p13 in PSAs

Table 49.3

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Feb 18, 2015 | Posted by in Oral and Maxillofacial Pathology | Comments Off on Salivary neoplasms
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