Salivary gland disorders are varied. Among them, tumors are rare, varied and can have serious consequences. These neoplasms account for 3 to 5% of all head and neck tumors, with an overall annual incidence ranging from 0.4 to 13.5 cases per 100,000 inhabitants [1]-[3]. Primary tumors of the salivary glands correspond to all primary benign or malignant cell proliferations developed at the expense of salivary tissues. They are largely dominated by epithelial tumors. Approximately two-thirds of salivary gland tumors (SGTs) are benign, compared to one-third that are malignant [1][2]. In developing countries, this condition remains a reality. In Senegal, the proportion of deaths due to salivary gland cancer (0.52% of all cancer deaths) is twice as high as the global average, which is 0.2% according to Globocan 2018 [4]. In our context, these tumors have been little studied in terms of anatomical-pathology. The anatomo-pathological examination occupies an essential place in the diagnosis, evaluation of the prognosis and treatment of salivary tumors.

In Senegal, these tumors have mainly been studied from a clinical and therapeutic perspective, focusing exclusively on the major salivary glands. We therefore conducted a study aimed at studying the epidemiological profile and histological forms of primary salivary gland tumors, as a whole, diagnosed in the pathological anatomy and cytology (PAC) laboratories of Dakar hospitals.

In our context, these tumors have mainly been studied clinically and therapeutically. We therefore conducted a study aimed at studying the epidemiological profile and histological forms of primary salivary gland tumors, as a whole, diagnosed in the pathological anatomy and cytology (PAC) laboratories of Dakar hospitals.

This is a retrospective, descriptive, multicenter study, over a period of 5 years (January 2014 to December 2018), at the level of all the pathological anatomy and cytology laboratories of the four University Hospital Centers (UHC) of Dakar. We based findings on the registers, archives of results and CAP examination reports. The parameters studied were age, sex, time of consultation, nature of the sample, location of the lesion, and histological type. We included all documented cases with a diagnosis of primary salivary gland tumor, confirmed on the basis of histological examination. We included all histological reports of patients diagnosed with primary salivary gland tumors, confirmed by histological examination, during the study period. These tumors were diagnosed and then classified or reclassified according to the 2017 WHO classification criteria for salivary gland tumors. [2] The selection was exhaustive. The data collected were entered using Excel software and analyzed with Epi info 3.5.4 software. The tables and figures were produced using Microsoft Excel 2016 and Word 2016 software. In the descriptive analysis, qualitative variables were described using frequency tables, bar charts, or pie charts. The quantitative variables were described by their position parameters (average, median and mode) and dispersion (Standard deviation, extremes).

During the study period, 145 cases of salivary gland tumors were recorded. The average age was 44.5 ± 18.7 years with extremes of 1 and 85 years. The mode and median were 52 and 45 years, respectively. Patients aged over 60 were the most represented (Figure 1).

Figure 1. Distribution of patients according to age groups.

The sex ratio (F/M) was 1.23. The duration of progression of the pathology was recorded in almost a third of the patients (N = 45). The average duration of progression was 5.6 ± 6 years with extremes of 0.25 and 30 years. The median was 3 years.

A large majority of patients, i.e. 89.65% (N = 130), had a tumor of the main salivary glands (MSG), compared to 10.34% (15 cases) of tumor of the accessory salivary gland (ASG). These tumors were mainly located in the parotid with 108 cases (74.5%), followed by the submandibular glands (SMG), i.e. 21 cases (14.5%) (Figure 2).

Tumors of the accessory salivary glands were located preferentially on the palate 53.33% (N = 8) and the cheek 26.6% (N = 4) (Table 1).

Figure 2. Distribution of patients according to site.

Table 1.Distribution of patients according to ASG site.

The distribution of the site of the SGT was almost similar according to the sex of the patients with a p value of 0.569 (Figure 3).

p-value = 0.569.

Figure 3. Distribution of the site according to the sex of the patients.

Surgical specimens constituted the main type of sample, i.e. 80% (N = 116). Biopsies represented 20% of cases (N = 29). The tumor was epithelial in nature in almost all patients (141 cases) or 97.2% of cases. The percentage of epithelial tumors was almost similar depending on the sex of the patients with a p value of 0.671 (Table 2).

Table 2. Distribution of the epithelial or non-epithelial nature of the tumor according to the sex of the patients.

More than half of the patients 60% (N = 87) had benign tumors and 40% (N = 58) malignant tumors.

Patients with malignant tumors were on average older than those with benign tumors (52.2 and 39.4 years, respectively). The difference was statistically significant with a p-value < 0.001 (Table 3).

Table 3. Distribution of malignant and benign tumors according to the average age of patients.

p-value < 0.001.

p-value = 0.484.

Figure 4. Benignity or malignancy according to the sex of the patients.

The proportion of benign tumors was higher in female subjects than in male subjects (62% and 56.3%). The opposite was observed for malignant tumors, with 38% for women and 43.7% for men. However, the difference was not statistically significant with a p value = 0.484 (Figure 4).

Tumors of the parotid (61.1%) and submandibular salivary glands (76.2%) were mainly benign, while those of the accessory salivary glands were mainly malignant (66,6%) (Table 4).

Table 4. Distribution of benignity or malignancy according to site.

Pleomorphic adenoma (PA) constituted the most frequent histological type in the series with 81 cases, or 55.8%, followed by mucoepidermoid carcinomas (MEC) and cystic adenoids (ACC) with 10.3 and 6.9% respectively (Table 5).

Table 5. Distribution of patients according to histological type.

NOS: Not otherwise stated/NOS: Not specific.

In our study, adenomas constituted the majority of benign epithelial tumors. The PA was the main benign epithelial tumor, accounting for 93.1%. MEC and ACC were respectively the second and third most frequent tumors, likewise they were the most common malignant tumors, respectively 25.8% and 17.24%.

The other most common malignancies were acinar cell adenocarcinoma, epithelial–myoepithelial carcinoma, carcinoma ex-pleomorphic adenoma, and polymorphic adenocarcinoma (Table 6).

Table 6. Distribution of the proportion of benign or malignant tumors according to histological type.

Average age and sex ratio varied considerably depending on histological type. Parotid localization dominated for all types (Table 7).

Table 7.Distribution of average age of patients, sex ratio and main site according to histological type of tumor.

According to literature data, SGT can occur at any age with a peak in the sixth and seventh decade, as shown in our study [1][2]. In Africa, several series, including ours, show an average age between the third and fifth decade. Very often he sex ratio varies considerably depending on the studies, in favor of the female sex. According to WHO 2005 [1], women are more frequently affected but there are variations depending on the histological type [1]. This female predominance could be due to the fact that women are more numerous in the general population but also in our context, they consult more often than men due to the aesthetic changes caused by the expression of these tumors (Table 8).

The consultation period is generally long, as evidenced by our series and several studies, notably those of Diouf K [17], in Senegal and Diom ES et al. [18], in Brazil that of Takahama et al. [19], in Tunisia, that of Brahim et al. [20], which showed an average duration varying between 2 and 6 years.

This long delay that is generally observed is related to the asymptomatic nature, especially painless, with a latent evolution of these pathologies. In addition, in Senegal there is poverty, the lack of health infrastructure contrasting with easy access to care from traditional practitioners.

SGT are more frequently of interest to MSGs. The parotid is the most common location, followed by SMG and ASG, as evidenced by the literature. (Table 9) GSLs are rarely affected. The majority of ASG are located in the palate [1][21], this may explain the preponderance of palatal ASG tumors.

Table 8.Comparison of the average age and sex ratio of TGS according to various series.

Table 9.Comparison of the location of TGS according to various series.

The tumors are often epithelial in nature and predominantly benign, this fact being corroborated by different series (Table 10).

Table 10.Proportions of benign and malignant tumors according to the authors.

Patients with malignant tumors are on average older than those with benign tumors, as noted by Ouedraogo AS [9], Oukabli et al. [8], Setti K et al. [23], who found an average age between 52.42 and 60 years for malignant tumors relatively higher than for benign tumors whose average age is between 34.05 and 43 years. Similarly, malignant tumors affect men more than women (43.8% vs 38%), corroborated by several studies. [6][15][23] The proportion of cancers is often much greater in the accessory salivary glands than in the main ones, as confirmed by our study. (Table 11) The frequency of malignant tumors would be inversely proportional to the size of the gland. It would be 20% - 30% in the parotid gland, 45% - 60% in the submandibular gland, 70% - 85% in the sublingual gland (SLG) and 49% - 80% in the accessory salivary glands [7].

Table 11.Proportions of malignant tumors according to location and authors.

PAis the most frequently encountered histological type, representing more than half of TGS, the first benign tumor, preferentially localized in the parotid and with a female predominance. These results are shared by several authors such as Bonfils P et al. [3], Archour I et al. [24]; Ouedraogo AS. [9]; Moartemri R et al. [6]; Illé S et al. [25] and El-Naggar et al. [26] who found a proportion of pleomorphic adenoma between 60% and 63% of all salivary tumors, associated with a female predominance.

MEC is the second most frequently found tumor, the first malignant tumor, preferentially localized in the parotid, with a large male predominance. This is consistent with several studies [1][6][18][26][27].

ACC is the third most frequently found tumor, the second malignant tumor, preferentially localized in the parotid, with a large male predominance. This is consistent with studies by El-Naggar et al. [26] and Badoual C et al. [27], in which ACCs account for just under 10% of SGTs and occur at all ages, with a peak frequency between 40 and 60 years of age. Other studies show that this histological type is the most common malignant tumor, with a female predominance, notably that of Setti K [23].

This work could present limits which we were able to identify as follows.

- Was a retrospective descriptive study.

- Parameters such as address, contacts, medical history, smoking, alcohol consumption, radiation exposure, occupation, and family history were often missing, preventing a search for risk factors through multivariate analysis.

- Our study was limited to determining the epidemiological and anatomopathological profile of salivary gland tumors in Senegal by comparing malignant tumors with benign ones.

- We were unable to carry out the immunohistochemistry and molecular biology techniques which would have allowed respectively better diagnostic accuracy, and molecular typing.

- We were unable to have the necessary hindsight to assess the prognosis and precisely the survival of our patients given the duration of the study and missing information. Nevertheless, our study presents positive points.

- This is a multicenter study and the first to take into account both tumors of the major and minor salivary glands and benign or malignant tumors, to our knowledge in Senegal, hence its originality.

Primary salivary gland tumors are relatively rare in Senegal and are often diagnosed late. Older people, men, and people with lesions of the accessory salivary glands are more prone to developing cancer in our context. In perspective, a prospective study including the risk factor analysis, molecular alterations, and assessment of patient survival based on histological type and treatment protocols will enable better prevention and optimized care, respectively.