Epidemiological and histopathological patterns of salivary gland tumors in Cameroon

Introduction Tumors of salivary glands are rare. According to Johns and Goldsmith in 1989, their annual incidence is less than 1/100000 without noteworthy geographical gap. But other authors suggest that their distribution may vary according to the race and geographical location. In Cameroon, existing studies give incomplete data. Hence, we underwent this study in order to draw the general profile of salivary gland tumors in Cameroon. Methods A retrospective study was carried out on the period spanning from January 2000 to December 2010 (11 years). It was done in nine Pathology services of different hospitals in Yaoundé, Douala and Bamenda. We consulted the archive registers of those services, retaining any patient with salivary gland tumor, whatever the histological type or location. Information gathered was the year of diagnosis, the service, the age and sex, the site of the tumor (gland) the histological type and the benign/ malignant character. Results We recruited a total of 275 files. Women were 56% (154/275) and men 44% (121/275) of the sample. Fifty eight tumors were malignant (21.9%) while 217 were benign (78.1%). The overall mean age was 37.44 years, with extremes between 1 and 84 years. Pleomorphic adenoma (60.36%) was the most common benign tumor. Adenoid cystic carcinoma (31%), mucoepidermoid carcinoma (22.4%) and adenocarcinoma (19%) were the most common malignant tumors. Palate (66.7%), cheek (30%) and lips (3.3%) were the sites were the minor salivary glands were mostly involved. Conclusion The differences with western world authors suggest a geographical variability of salivary gland tumors.


Introduction
The tumors of salivary glands are rare [1][2][3]. According to Johns and Goldsmith in 1989, their annual incidence is less than 1/100000 inhabitants, without noticeable geographical gap andthey represent less than 5 % of head and neck tumors [1]. It is postulated in the western world literature that their distribution is about 100:10:10:1 for parotid gland, sub maxillary gland, accessory salivary glands and sublingual gland respectively [2]. But recent African studies found a distribution of 1:1:1 for parotid, sub maxillary and accessory salivary glands respectively [3]. In Cameroon, existing data are partial because they are gland specific or on limited study samples. We therefore undertook this study in order to study the main histopathological and epidemiological features of the tumors of salivary glands in Cameroon.

Methods
We carried out a retrospective, descriptive and multicentric study on

Results
We recruited a total of 275 files from the nine hospital centers.
There was an increase of the number of cases per year as from  (Table 3). We compared our results to those of other authors. It shows a similarity between African results, contrary to Western World literature (Table   4).

Discussion
There is a boom of tumoral diseases in Africa in general and Cameroon in particular. It is estimated that 12,000 to 14,000 new cases are diagnosed each year in the Country [5,6]. Tumours of head and neck follow the same progression. In this retrospective work on the tumors of salivary glands, we found a predominance of  [2] found in Ouganda and Congo respectively. It was higher than the 30 years found by Bahiru [7], what he explained by the fact that in those regions persons of the third age are more attracted to alternative medicines. The age range most affected by malignant salivary gland tumors was the 60 and above (24.1%). Evesonet al found a peak of malignant tumors at 70 years [9]. The 20-30 age range was the most affected by benign tumors (27.2%). It is younger compared to the findings of Eveson [9] and Onyango [11] who found peaks of incidence at 60 and 40-59 years respectively. These differences suggest a variation of the distribution of those tumors according to the site, due to different influencing factors. Especially, the longer life expectancy, the development of means of prevention and the better quality of life in the western world [12].
Women were predominant in the sample, with a male/female sex ratio of 0.78. Kayembein Congo and Vuhahula in Ouganda found similar results with 0.8 and 0.76 respectively [2,10].This predominance can be due to the women's tendency to better care about their cosmetic appearance, thus seeking more often medical help when a tumor deformity appears. Malignant tumors also predominate in the women (51.7%). It was also found by Vuhahula (52.4%), unlike Ben Brahimand El-Gazayerliwho instead found the predominance in males [8,13].
There was a predominance of benign tumors (78.1%). This was similar to the results of Ben Brahim [13] and Ouoba [14] with respectively 88.3% and 83.3% of benign tumors. Vuhahula [2] and Masanja [15] found an almost equal distribution : 54% of benign tumors and 46 % of malignant tumors. This is due to the fact that in our study, the regions concerned have a good health coverage and the health personnel performs surgery straightaway in front of a clinical suspicion of benign tumor, surgery easily accepted by the patients in this context, contrary to when malignancy is suspected, then preferring traditional medicine. The benign tumors could also have been over diagnosed in our sample since some of the pathological characteristics of pleomorphic adenomas are similar to those of carcinomas. So, some pathologists here as elsewhere classify low grade malignant tumors in the benign tumors [4,16]. In addition to that, immunohistochemical methods of pathology diagnosis are not yet used in the study centers.
Proportionally in this study, the parotid gland is less often the site of tumor (49%) than in the western studies (70%) [16], while the submandibular gland is more often, with 39% versus 10-15% [1]. This has been found by other African authors [2,14]. Some like Aboul Nasr (1961) emitted the hypothesis that endemic parotiditis could decrease the susceptibility of parotid gland and increase that of the submandibular gland to neoplasms [8]. El-Gazayerli et al. also noticed that malnutrition altered more the serous cells than the mucous, thus decreasing the susceptibility of parotid gland to neoplasms [8].
Pleomorphic adenoma represented 47.7% of the tumors of salivary glands, being the first. This is constant finding for all the authors.
Masanja and Vuhahula found similar proportions of 44.4% and 40.9% respectively [2,15], contrary to Ben Brahim (61.7%) [13] and Bahiru (58.5%) [7]. The cystic adenoid carcinoma was the most frequent malignant (6.6%), followed by the mucoepidermoid carcinoma (4.7%). Vuhahulain Ouganda, Kayembe [3,10], while in western countries it accounts for 5 to 20% of all tumors of salivary glands [2]. The young age of African patients has been advanced to explain the gap [8]. But this argument is not sufficient since the age range of their peak in African series contains the mean age of Western World series [2].
Twenty two per cent of the tumors of accessory salivary glands were malignant. Ben Brahim found a lower proportion of malignancy, 9.1%, contrary to western literature which reports as much as 50% of tumors of those glands being malignant [16]. We have no explanation to this difference. The limits of this study are its inability to clearly discriminate the factors influencing the distribution of salivary gland tumors, since we didn't have sufficient data to run parametric tests.

Conclusion
This study shows a distribution of salivary gland tumors different from that of western countries and aligning with other African authors, strengthening the hypothesis that salivary gland tumor present with regional variations which could be related to endemic infections and nutritional factors amongst other things. But prospective studies need to be carried out on bigger samples in order to better discriminate the influencing factors.
What is known about this topic?
• Salivary gland tumors are rare.
• 80% of the tumors arise from the parotids.

What this study adds
• Parotid/submandibular ratio is 1.23.

Competing interests
The authors declare no competing interests.

Acknowledgments
We are grateful to the Heads of the contributing Pathology services for their warm welcome and help during the data collection of this study.        This group was dominated by benign tumours.

Tables and figure
The inflammatory pseudo tumor represented 55.67% of them. We noticed a rarity of Wharthin's tumor in the majority of African studies as well as a very low parotid/submandibular ratio.
Page number not for citation purposes 8 Figure 1: Distribution of patients according to age range and histology; the red line represents the slope of the frequency of malignant tumors