Leukoplakia and tobacco habits in Gizan, Saudi Arabia

 
The prevalence of leukoplakia in relation to tobacco habits was studied in 1,436 subjects in a population of 16,400 at Gizan Region, Saudi Arabia. The prevalence rate of oral leukoplakia and preleukoplakia in this study were 11.4% and 4.3%, respectively. Of the affected subjects, 99% were dippers of snuff known as Shamma. it is a powdered tobacco mixed with sodium carbonate hemihydrate in a ratio of 3:1 by weight.
The location of the oral lesion was almost always consistent with the site where the snuff was habitually held. A smaller proportion of lesion was found in Shisha smokers while none of those who only smoked cigarettes had leukoplakia or preleukoplakia.
The findings of this study provide evidence that a relationship exists between oral leukoplakia and Shamma dipping.

 
Gizan province occupies the Southwestern corner of Saudi Arabia covering an area of about 20,000 km2. It is one of the most densely populated parts of the Kingdom with an average population of 700,000, constituting approximately 6% of the total population of Saudi Arabia.1 Eighty-seven percent of the population resides outside the town in more than 4,500 villages.
Oral cancer is a major health problem of the population in Gizan, comprising 33% of all cases of malignancy received in one year at King Fahad Hospital.2,3 Previous studies2-4 have pointed out that oral cancer in Gizan was always associated with oral leukoplakia and also confirmed the relationship between oral cancer and tobacco habits, particularly dipping the type of snuff known as Shamma.
Shamma is a mixture of powdered tobacco and sodium carbonate hemihydrate in a ratio of 3:1 by weight.2 The quid is placed in the lower labial or buccal vestibules, allowing absorption of the active ingredients through the oral mucosa. Although prohibited by law, Shamma dipping is practiced by both sexes in the rural areas of Gizan.
Oral leukoplakia had been reported as the most precancerous lesion of the mouth in the Southeast Asia subregion.5-8 The rate of malignant transformation in oral leukoplakia varied from 4-6% in some studies9 to even higher figures in others10.
The aim of this study was to report on the prevalence of oral leukoplakia and allied lesions in relation to tobacco habits among the population of Gizan.

 
The study material comprised 1,436 male and female subjects, aged 20-57 years, among 16,400 residents of Gizan town, an area of 720 km2.
All subjects were registered and matched as to age and sex. Examination took place in day-light with the subject sitting on an ordinary chair. The criteria for inspection of the oral mucosa and for the diagnosis of the oral lesions were applied according to the definitions of the World Health Organization (WHO) Collaborating Center for Oral Precancerous Lesions.11,12 Leukoplakia was diagnosed as "an elevated white patch of the oral mucosa measuring 5 mm or more which cannot be scraped off, and which cannot be attributed to any other diagnosable disease".12 Preleukoplakia was diagnosed as a grayish white area measuring 5 mm or more with indistinct borders on the oral mucosa.12 The location of the lesion was designated using the recommendations of Roed-Petersen and Renstrup for the topographic classification of the oral mucosa.13 All examinations were done by the same examiner. Sixteen biopsies were obtained from four preleukoplakia and twelve leukoplakia patients, who were clinically diagnosed. All biopsies were taken from the buccal mucosa proper under local anesthesia. The specimens were fixed in 10% buffered formosalin, embedded in paraffin, cut serially and stained with hematoxylin and eosin, periodic acid Schiff (PAS) reagent and a modified Mallory stain.
All subjects were then interviewed individually by another member of the team as to their tobacco habits. The sites where Shamma dippers placed the quid were identified and plotted on a diagram in the patient's record.

The age and sex distributions of the population examined are shown in Table 1. Mucosal lesions compatible with leukoplakia or preleukoplakia were diagnosed in 15.7% of the population examined. Leukoplakia was evident in 11.4% while preleukoplakia was identified in 4.3%. The prevalence of leukoplakia and preleukoplakia among the population examined is shown in Table2.
The anatomical distribution of the oral lesions is shown in Table 3. Location of the lesion was almost always consistent with the site where Shamma was habitually held.
Three morphological variants of leukoplakia were identified, namely homogenous [Fig. 1], verrucous [Fig. 2], and speckled or erosive forms [Fig. 3]. The distribution of the morphological variants of leukoplakia is shown in Table 4.
All individuals with mucosal lesions were Shamma dippers, however, others smoked cigaret-tes or Shisha. The relationship between tobacco habits and mucosal lesions is shown in Table 5.
The four biopsies from preleukoplakia areas did not show a consistent histologic pattern although a parakeratotic surface layer was found in two specimens. In the twelve biopsies of leukoplakia, six were from patients diagnosed for the homogenous type. Sections showed epithelial hyperplasia, acanthosis, hyperorthokeratosis, well-developed granular layer, and mild inflammatory cell infiltra­tion of the connective tissue [Fig. 4],
Three biopsies were obtained from verrucous leukoplakias. These showed epithelial hyperplasia, acanthosis, mild hyperorthokeratosis, with an underlying granular layer and minimal infiltration in the connective tissue. In these areas partial hyperorthokeratosis was noted [Fig. 5). The three biopsies from erosive leukoplakias revealed hyperplastic epithelium, surface ulceration, parakeratosis and a prominent inflammatory cell infiltration of the underlying connective tissue [Fig.6]
 

 
In this study, oral leukoplakia was clinically diagnosed on the subjects in accordance with WHO's recommendations.11,12 Biopsies were taken in only sixteen cases for confirmation of mucosal lesions. The prevalence rates of leukoplakia and preleukoplakia in this study were 11.4% and 4.3%, respectively. These figures are among the highest reported so far as compared with the similar studies from different parts of the world.14-17 Table 6 shows comparable prevalence rates from four countries.
In this study, it was evident that there was an increase in the frequency of leukoplakia and a relative decrease in preleukoplakia with advancing age. It is also evident that while the frequency of leukoplakia in general appeared to increase with advancing age, erosive leukoplakia predominated among the older age group. It is generally agreed that the rate of malignant transformation in erosive leukoplakia is high.8-10
Among the 226 subjects who dipped Shamma, 98.7% had leukoplakia or preleukoplakia (Table 5). When these findings were compared with other tobacco habits, no association was evident between smoking cigarettes or Shisha and the development of oral lesions. Leukoplakia was not clinically diagnosed in patients who did not have Shamma dipping habit.
In summary, this report points out the association between leukoplakia and/or preleukoplakia and Shamma dipping in this part of Saudi Arabia. Microscopic study was minimal and larger part of the study was clinical. The findings provide the evidence, in support of a preventive program designed for early detection of precancerous oral mucosal diseases in Saudi population, that at risk in the Gizan province of the Kingdom.