Definition

 It is a rare, usually well-circumscribed tumour composed of irregularly sized and shaped nests of sebaceous cells without cytologic atypia, often with areas of squamous differentiation and cystic change.

ICD-O code 8410/0

Epidemiology

They account for 0.1% of all salivary gland neoplasms and slightly less than 0.5% of all salivary adenomas {2301}. The mean age is 58 years (22-90 years) and the male:female ratio is 1.6:1 {896, 901}. Unlike cutaneous sebaceous neoplasms {1132,2214}, there is no increased risk of developing a visceral carcinoma.

 Localization

Approximately 50% of tumours arise in the parotid gland, 17% in the buccal mucosa, 13% in the retromolar region or area of the lower molars and 8% in the submandibular region {896}.

 Clinical features

Patients typically present with a painless mass.

Macroscopy

These adenomas range in size from 0.4- 3.0 cm in greatest dimension, are commonly well circumscribed to encapsulated and are greyish-white to yellow {896,901}.

 Histopathology

They are composed of sebaceous cell nests often with areas of squamous differentiation with minimal atypia and pleomorphism with no tendency to invade local structures. Many tumours are microcystic or composed predominantly of ectatic ductal structures. The sebaceous glands frequently vary markedly in size and tortuosity and are often embedded in a fibrous stroma. Occasional tumours demonstrate marked oncocytic metaplasia. Histiocytes and/or foreign body giant cells can be seen focally. Lymphoid follicles, cytologic atypia, cellular necrosis, and mitoses are usually not observed. Infrequently, these tumours may be part of a hybrid neoplasm {2297}.

Treatment and prognosis

Treatment consists of complete surgical excision. They do not recur.