Q&A: What are oral potentially malignant disorders?
Author: Sanketh DS, MDS
Certain red and white mucosal lesions/conditions in the oral cavity have been identified to have a potential to undergo malignant transformation to oral squamous cell carcinoma(OSCC). This has been reported in several longitudinal studies, where many such red/white lesions have undergone malignant transformation on subsequent follow-up. Also, several researches have reported the presence of genetic and molecular alterations in these lesions, the likes of which are also found in early invasive OSCCs. Hence, in 1978, WHO termed such clinical manifestations as “oral precancer” and broadly classified them as “precancerous lesions” and “precancerous conditions”.
A precancerous lesion was defined as “a morphologically altered tissue in which oral cancer is more likely to occur than in its apparently normal counterpart” and a precancerous condition is “a generalized state associated with a significantly increased risk of cancer”. These presentations were so classified because, it was thought that oral cancer arising from a “precancerous lesion” would arise in the same location as the lesion, and malignancy from a “precancerous condition” could arise in any anatomic location of the mouth or pharynx.
However, the use of the term “precancer” would mean, that all such lesions/conditions would inevitably transform to OSCC, which is not true. It is known that, not all but only some among these red/white manifestations may have a potential for malignant transformation. Hence, WHO in 2005 relabelled “precancer” as “potentially malignant” since the word “potential” literally means “having possibility” or “capable of being but not yet in existence”.
It is also known that OSCCs arising from precancerous lesions, need not necessarily arise from the same site as the lesion and that even other clinically normal sites in the oral cavity could harbour genetic alterations and manifest with dysplasia and subsequent malignancy. Hence, WHO did not approve of classifying these lesions as precancerous lesions and conditions and rather termed all red/white presentations having a risk of becoming OSCC as “Oral Potentially Malignant Disorders”.
Thomson P.Oral Precancer – Diagnosis and management of potentially malignant disorders. Blackwell Publishing Ltd;2012.
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