Epidemiology of Head & Neck Precancer
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Prevalence rates (per 1,000 adults) for oral leukoplakia in U.S. and European populations.

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How Common are Oral Precancers?

Incidence rates. No Western study has determined incidence for oral leukoplakia, although in India new lesions have been shown to occur in 0.8/1,000,000 persons annual, compared to an oral cancer incidence rate in the same population of 5/1,000,000. It is not known or assumed that all oral cancers in India arise from leukoplakic lesions, but a large proportion of them probably do so. In the U.S., Bouquot et al attempted to determine the leukoplakia incidence in the predominantly white community in which the Mayo Clinic resides, but were unable to do so because data from local dentists could not be compiled.

Likewise, no good incidence data are available for oral erythroplakia, but incidence investigations of oral/pharyngeal carcinoma in situ, which represents the vast majority of erythroplakias, have determined that only six cases are diagnosed per one million persons each year.

The only other head and neck precancerous lesions for which epidemiologic data are available are laryngeal keratosis (leukoplakia of vocal cords) and laryngeal carcinoma in situ. These lesions are diagnosed annually in 5.8 and 0.4 persons per 100,000 population.

Prevalence Rates. Since the 1950s a number of reports have indicated that at least the most common form of oral premalignancy, leukoplakia, is quite common indeed (Table 2), and that it represents one of the five most common chronic diseases affecting the oral mucosa. More recent studies have been especially careful to eliminate frictional keratosis and smokeless tobacco keratosis from their collections of true leukoplakia, and so the prevalence has been reduced somewhat from 3-4% of an adult Western population to 1-2%. Even at 1% of the adult population, however, it can be estimated that 1,800,000 Americans are afflicted with this premalignancy.

Smokeless tobacco keratosis has a much lower malignant transformation potential than leukoplakia, but in some populations where the habit of chewing tobacco is popular, lesions can be found in up to 9% of males.

Oral lichen planus, a questionable precancer, affects one of every 1,000 adults in Western populations; in certain subpopulations it is seen as often as once per 32 persons.

Are Some Worse Than Others?

Predicting the risk of malignant transformation of any particular precancer of the head and neck region is a formidable task.  The tremendous number of potential influencing factors and cofactors, along with great differences in study design and disease definitions, has led to considerable confusion on this subject.  Nevertheless, it is important to at least make the effort to establish or estimate relative risk, and to this end the following table provides a "best guess" relative risk for the various types of oral precancers.

Table 1: Estimated relative risk of developing oral cancer from various oral precancers.

Reference: Modified from: Bouquot JE. The pathology and progression of oral premalignancy. Proceedings, Epithelial Dysplasia Symposium, 5^th International Congress on Oral Cancer, Royal College of Physicians, London, United Kingdom; September, 1997.

  # reverse smoking: smoking with the lit end of the cigarette in one's mouth

Tables for Specific Precancers

Click on table number (if underlined) to see data for specific lesions.

Table 2: Prevalence rates (per 1,000 persons) for oral leukoplakia, listed by date of publication. 

References are at end of this page, listed by date of publication.

Table 3: Prevalence rates (per 1,000 persons) for erythroplakia of the oral mucosa.

References are at end of this page, listed by date of publication.

Table 4: Average annual incidence rates (per 100,000 persons/year) for carcinoma in situ of various head and neck anatomic sites. Population base: males = 900,312 person-years; females = 1,102,916 person-years).

Reference: Bouquot JE, Kurland LT, Weiland LH. Carcinoma in situ of the upper aerodigestive tract: incidence, time trends and follow-up in Rochester, Minnesota, 1935_1984. Cancer 1988; 61:1691-1698.

Table 5: Average annual incidence rates (per 100,000 persons/year) for laryngeal keratosis (leukoplakia), carcinoma in situ and invasive carcinoma of the larynx. Population base: males = 900,312 person-years; females = 1,102,916 person-years).

References: Bouquot JE, Weiland LH, Kurland LT. Laryngeal keratosis and carcinoma in the Rochester, Minnesota population, 1935-1984. Cancer Detect Prevent 1991; 15:83-91. Bouquot JE, Gnepp DR. Laryngeal precancer -- a review of the literature, commentary and comparison with oral leukoplakia. Head Neck 1991; 13: 488-497.

Table 8: Gender-specific prevalence rates for all mucosal, soft tissue and bony oral and oropharyngeal lesions clinically diagnosed in 23,616 white U.S. adults (97% whites; 8,477 males, 15,139 females) over 35 years of age, ranked by total prevalence. 

References: Modified and extended from Dr. Bouquot's earlier published papers.

* NOS = not otherwise specified; all cases biopsy proven and included in leukoplakia rates, except the single case of basal cell carcinoma of the vermilion border.

References, Dr. Bouquot's Prevalence Data

Bouquot JE. An Epidemiologic Evaluation of Oral Carcinoma, Premalignant Epithelial Dysplasia and Nonspecific Clinical Keratoses in an Adult Minnesota Population of 23,616. Master's Thesis, University of Minnesota Graduate School, 1974, pp 1-96.

Bouquot JE. Common oral lesions found during a mass screening examination. J Amer Dent Assoc 112:50-57, 1986.

Bouquot JE, Gorlin RJ. Leukoplakia, lichen planus and other oral keratoses in 23,616 white Americans over 35 years of age. Oral Surg Oral Med Oral Pathol 1986; 61:373-381.

Bouquot JE, Gundlach KKH. Oral exophytic lesions in 23,616 white Americans over 35 years of age. Oral Surg Oral Med Oral Pathol 1986; 62:284-291.

Bouquot JE, Gundlach KKH. Odd tongues: the prevalence of common tongue lesions in 23,616 white Americans over 35 years of age. Quint Internat 1986; 17:719-730.

Bouquot JE. Epidemiology. In: Gnepp DG. Pathology of the head and neck. New York: Churchill Livingstone, 1987, pp 263-314.

Bouquot JE, Gundlach KKH. Odd lips: the prevalence of common lip lesions in 23,616 white Americans over 35 years of age. Quint Internat 1987; 18:277-284.

Bouquot JE, Crout RJ. Odd gums: The prevalence of common gingival and alveolar lesions in 23,616 white Americans over 35 years of age. Quint Internat 1988; 19:747-753.

References: Epidemiology of Oral Premalignancy 
(including Carcinoma in Situ)

Note: Click on underlined author(s)'s name to see abstract, summary or full paper

Gerry RG, Smith ST, Calton ML. The oral characteristics of Guamians including the effects of betel chewing on the oral tissues. Oral Surg Oral Med Oral Pathol 1952; 5:762-781.

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Atkinson L, Chester IC, Smith FG, et al. Oral cancer in New Guinea: a study in demography and etiology. Cancer 1964; 17:1289-1298.

Forlen HP, Hornstein O, Stuttgen G. Betelkauen und Leukiplakie. Arch Klin Exper Dermatol 1965; 221:463-480.

Pindborg JJ, Chawla TN, Misra RK, et al. Frequency of oral carcinoma, leukoplakia, leukoedema, leukokeratosis, submucous fibrosis and lichen planus in 10,000 Indians in Lucknow, Uttar Pradesh, India. J Dent Res 1965; 44:615-618.

Pindborg JJ, Kalapessi HK, Kale SA, et al. Frequency of oral leukoplakias and related diseases among 10,000 Bombayites. J All India Dent Assoc 1965; 37:1-2.

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Zachariah J, Matthew B, Varma NAR, et al. Frequency of oral mucosal lesions among 5,000 individuals in Trivandrum, South India. J All India Dent Assoc 1966; 38:290-294.

Pindborg JJ, Rhatt M, Devanath KR, et al. Frequency of oral white lesions among 10,000 individuals in Bangalore, South India. Indian J Med Sci 1966; 20:349-352.

Pindborg JJ, Barmes OD, Roed-Petersen B. Epidemiology and histology of oral leukoplakia and leukoedema among Papuans and New Guineans. Cancer 1968; 22:379-384.

Jussawala DJ, Rajpal RN. Leukoplakia: Proceedings of the symposium on precancer. Bulletin #39, New Dehli: National Inst Science India 1969:19-27.

Mehta FS, Pindborg JJ, Gupta PC, et al. Epidemiologic and histologic study of oral cancer and leukoplakia among 50,915 villagers in India. 1969; 24:832-849.

Wahi PN, Mital VP. Epidemiological study of precancerous lesions of the oral cavity: a preliminary report. Indian J Med Res 1970; 58:1361-1491.

Bouquot JE. An Epidemiologic Evaluation of Oral Carcinoma, Premalignant Epithelial Dysplasia and Nonspecific Clinical Keratoses in an Adult Minnesota Population of 23,616. Master's Thesis, University of Minnesota Graduate School, 1974, pp 1-96.

Sonkodi TK. Szegedi textitipari munkasok stomato-onkologiai vizgalata. Fogorv Sz 1974; 67:165-169.

Axéll T. The relation of the clinical picture to the histopathology of snuff dipper's lesions in a Swedish population. J Oral Path 1976; 5:229-236.

Mehta FS, Pindborg JJ, Bhonsle RB, Sinor PN. Incidence of oral leukoplakia among 20,358 Indian villagers in a 7-year period. Br J Cancer 1976; 33:549-554.

Silverman S, Bhargava K, Mani N, et al. Malignant transformation and natural history of oral leukoplakia in 57,518 industrial workers of Gujaret, India. Cancer 1976; 38:1790-1795.

Wilsch L, Hornstein OP, Bruning H, et al. Orale Leukopkein II. Ergebnisse einer 1 jahrigen poliklinischen Pilotstudie. Dtsch Zahnarztl Z 1978; 33:132-142.

Gupta PC, Mehta FS, Daftary DK, et al. Incidence rates of oral cancer and natural history of oral precancerous lesions in a 10-year follow-up study of Indian villagers. Community Dent Oral Epidemiol 1980; 8:287-333.

Winn DM, Blot WJ, Shy CM, et al. Snuff dipping and oral cancer among women in the southern United States. New Eng J Med 1981; 304:745-749.

Lay KM, Sein K, Myint A, et al. Epidemiologic study of 6,000 villagers of oral precancerous lesions in Bihigynn: preliminary report. Community Dent Oral Epidemiol 1982; 10:152-155.

Zachariah J, Pindborg JJ. Unpublished material as quoted in Pindborg JJ. Oral precancer. In: Barnes L (ed). Surgical pathology of the head and neck. New York: Marcel Dekker, 1985:279-331.

Bouquot JE, Gorlin RJ. Leukoplakia, lichen planus and other oral keratoses in 23,616 white Americans over 35 years of age. Oral Surg Oral Med Oral Pathol 1986; 61:373-381.

Axell T. Occurrence of leukoplakia and some other oral white lesions among 20333 adult Swedish people. Community Dent Oral Epidemiol 1987; 15:46-51.

Bouquot JE. Epidemiology. In: Gnepp DR (ed). Pathology of the head and neck. Philadelphia: Churchill-Livingstone; 1988: 263-314.

Bouquot JE, Weiland LH, Kurland LT. Leukoplakia and carcinoma in situ synchronously associated with invasive oral/pharyngeal carcinoma in Rochester, Minnesota, 1935-1984. Oral Surg Oral Med Oral Pathol 1988; 65:199-207.

Bouquot JE, Gnepp D. Epidemiology of carcinoma in situ of the upper aerodigestive tract. Cancer 1988; 61:1685-1690.

Bouquot JE, Kurland LT, Weiland LH. Carcinoma in situ of the upper aerodigestive tract: incidence, time trends and follow-up in Rochester, Minnesota, 1935-1984. Cancer 1988; 61:1691-1698.

Bouquot J, Weiland L, Ballard D, Kurland L. Leukoplakia of the mouth and pharynx in Rochester, MN, 1935-1984; incidence, clinical features and follow-up of 463 patients from a relatively unbiased patient pool. J Oral Path 1988; 17:436.

Hogewind WFC. Oral leukoplakia in a Dutch population; a clinical study. Thesis. Amsterdam: Vrije Universiteit te Amsterdam, 1990:1-175.