SALIVARY GLAND TUMOURS
Tumours at this site occur with a frequency of about 1 per 100,000 population. They are commoner in Spanish, Inuit, Indian, and Cantonese Chinese populations, but do not appear to have a strong genetic basis. Familial occurrence of mixed salivary Tumours has been reported infrequently (Klausner and Handler 1994), and it is difficult to know whether the familial incidence is determined by hereditary or environmental factors. However, similarities in the epidemiology of nasopharyngeal carcinoma and salivary gland Tumours suggest that they may have a similar etiology, perhaps involving Epstein–Barr virus (EBV) infection (Ponz de Leon 1994). Several Greenland Inuit families have been described with two or more siblings affected, and there was an increased risk of other cancers in these sibships (Merrick et al. 1986). Other studies from Greenland show that a significant fraction of all cases occurring among Greenland Inuit clusters in families (Albeck et al. 1993). Cancer incidence in this part of the world differs from that seen in more temperate climates: compared to the Caucasian population in Denmark (1973–1995), high standardized incidence ratios (SIRs) were found for cancers of the salivary gland and nasopharynx (EBV-related cancers), esophagus, stomach (probably related to a dried fish diet), and cervix (HPV-related). Low SIRs were seen for testis, bladder, prostate, breast, and hematological cancers (Friborg et al. 2003). In a further study in the same population, there was about an eightfold increased risk of salivary gland carcinoma in first-degree relatives of patients with nasopharyngeal carcinoma (none of the salivary gland carcinoma patients developed
subsequent nasopharyngeal carcinoma in the follow-up period) (Friborg et al. 2005).
A single two-generation Inuit family from northern Quebec (Nunavik) that contained four family members of both sexes, all diagnosed with lymphoepithelioma of the parotid gland (without involvement of the nasopharynx), has been reported (Vu et al. 2008). Rare families with familial neuroendocrine carcinoma of the salivary glands and deafness and enamel hyperplasia (siblings) are described (Michaels et al. 1999).
MALT lymphomas may occur in the lymphoid tissue of the salivary glands, often associated with a translocation t (14:18 [q.32;q.21]) (Streubel et al. 2003). MALT lymphomas may develop in benign lesions developing from
long-standing Sjogren’s syndrome. There has been a case report of a 3-year- old child with a plexiform neurofibroma involving the submandibular salivary gland that mimicked an intraglandular Tumours (Bourgeois et al. 2001). There was a family history of neurofibromatosis.
Germline mutations in the CYLD1 gene may cause Brooke–Spiegler syndrome, familial cylindromatosis, and multiple familial trichoepithelioma 1. Salivary gland Tumours (adenomas and adenocarcinomas) may be a feature of these disorders (Kakagia et al. 2004; Bowen et al. 2005).