It is well recognized that the progression of a potentially malignant lesion to frank oral squamous cell carcinoma is not a singular event, but a gradual process of morphologic, genetic and histological aberrations that lead to malignant transformation. The occurrence of two or more lesions in a patient at the same time is termed as synchronous lesion, whereas lesion occurring after a three-month post-op period is called as a metachronous lesion [10].

In the present study, it was noted more males (78%) present with OPMD than females (22%) with buccal mucosa being the most commonly affected primary site. The most commonly noted OPMD in the present study was homogenous leukoplakia. Fernanda Weber Mello et al. [11]. performed a systematic review on prevalence of oral potentially malignant disorders worldwide and noted that the most common OPMD was oral submucous fibrosis (4.96%) and males were affected [11]. In this study, a majority of patients presented with mild (40%) and moderate dysplasia (36%).

Speight M et al. evaluated the risk factors that favour the progression to OPMD to malignancy and stated that factors like sex; site and type of lesion; habits, such as smoking and alcohol consumption; and the presence of epithelial dysplasia on histological examination dictated the transformation to malignancy [10]. In the present study, buccal mucosa was the affected site by the second OPMD following excision of primary lesion. Second OPMD refers to the incidence of metachronous recurrence of OPMD at the primary site or another new site. Patients with smoking tobacco habit exhibited the maximum occurrence of a second OPMD compared to smokeless tobacco (50%). However, findings by Jani et al. suggest that tobacco consumption in any form is hazardous and causes various kinds of oral premalignant lesions and people with exposure to tobacco are 43.62 times at higher risk of developing OPMD in the oral cavity [12].

The overall prevalence of a second OPMD other than the primary site was 26% in the present study; ie.13/50 patients (26%) had second oral potentially malignant lesion other than the primary site. Studies evaluating the malignant transformation rates of OPMD have been performed, but there is no literature available that describes the occurrence of second OPMD following excision of primary lesion. The occurrence of OPMD at another site can be explained by the concept of field cancerization. Repeated and constant exposure of carcinogens to the aerodigestive tract will predispose the individual to develop isolated or multiple-site lesions as described by Slaughter [5]. The concept of field cancerization proposes that the normal tissue adjacent to neoplastic region contains genetic markers which can, overtime, lead to recurrence of a second primary lesion [5, 13].

Thomson et al. performed a retrospective clinico‐pathological analysis on 590 patients with oral potentially malignant disorders. It was observed that (16.8%) developed cancer, 67.9% of lesions arose at new sites, 42.3% of cases showed micro‐invasive arising from severely dysplastic precursors. The most common sites of recurrence of the lesions was the ventro‐lateral tongue and the floor of mouth [14]. However in the present study, 4/50 (8%) of the cases showed micro-invasion out of which half of them (2 out of 4 patients) showed malignant transformation. The most common site of the second OPML lesion in the present study was the buccal mucosa.

Systematic review on potentially malignant disorders and dysplasia by Iocca O et al. showed that moderate/ severe dysplasia bears a much higher risk of cancer evolution than mild dysplasia [15]. These findings were consistent with the observations from the present study where 50% of the individuals with moderate dysplasia developed a second OPMD at another site.

In the present study, buccal mucosa exhibited the maximum new OPMDs. Pei-Shan Ho et al. conducted a retrospective cohort study on malignant transformation of oral potentially malignant disorders in males and observed that the rate of transformation was highest in subjects diagnosed with oral epithelial dysplasia with tongue being 2.41 times at more risk when compared with buccal lesions [16]. In the present study sites like the tongue (n = 1), the hard palate (n = 1) and alveolar mucosa (n = 1) showed malignant transformation.

While it is impossible to predict the behaviour of premalignant lesions on the basis of clinical appearance, histopathological features or predict the occurrence of a second OPMD, it is well evident that routine and aggressive follow-up protocols is earliest way for prompt detection of such lesions and treat it with minimum morbidity. This ensures secondary level of prevention of these lesions and its malignant transformation. Patients have to be counselled for their oral abusive habit which can significantly reduce the need for aggressive pharmacotherapy and significantly decrease the risk of transformation [17, 18].

In the present study, wide local excision of all lesions with one-centimetre margins in all dimensions was performed which is unlike the routinely recommended 5 mm margins for potentially malignant oral disorders. We postulate that resecting these lesions with adequate margins and reconstructing with local flaps reduces the chance of recurrence. The rate of recurrence of the lesions at the primary site was 4% (2/50 patients). Also, if the histopathological report is suggestive of malignancy/micro-invasion, this approach eliminates the need for re-excision of lesion. Regular self-evaluation and self-oral examination along with professional evaluation allows for early diagnosis of recurrent lesions.