To explain in layman term, these are lesions and/or condition may  have chances of transforming into oral cancer. Average age for occurrence of PMD's is  50–69 years, which is 5 years before occurrence of oral cancer. Unfortunately, in recent years 5% of PMDs has been observed in persons under 30.

PMD's are usually found on the buccal mucosa, followed by gingivae, tongue and floor of the mouth. World Health Organisation has classified PMDs into two types:

  • Premalignant Lesions: a benign lesion with morphologically altered tissue, which has a greater than normal risk of transforming into malignancy. These include:
    Proliferative verrucous leukoplakia(PVL)
    Candida leukoplakia
    Reverse smokings’ palate
    Verrucous hyperplasia
    Oral verrucous carcinoma
    Dyskeratosis congenita
    Actinic cheilosis
    Oral submucous fibrosis
  • Premalignant Conditions: a disease or patients’ habit that does not necessarily alter the clinical appearance of local tissues but is associated with a greater than normal risk of precancerous lesion or cancer development in that tissue. These include:
    Lichen planus
    Discoid lupus erythematosus
    Epidermolysis bullosa
    Cheilitis glandularis
    Xeroderma pigmentosum
    Plummer Vinson Syndrome
    Syphilis (third stage)
    Vitamin A, B, C deficiency
    Immunosuppressive disease (AIDS)

Oral PMD's are usually misdiagnosed due to lack of adequate knowledge among the general population and even medical professionals. 

Many oral cancers develop from PMDs, hence early diagnosis of these lesions  and associated risk factors can help save many lives form claws of cancer.