Oral leukoplakia, clinically classified as homogeneous or non-homogeneous (1), is one of the most common potentially malignant disorders (2, 3)[REMOVED HYPERLINK FIELD]. The non-homogeneous type presents a white surface with verrucous, nodular, ulcerated or erythematous features, all including a greater risk of malignant transformation than homogeneous types (1).
Nodular leukoplakia, firstly described as speckled leukoplakia by Pindborg et al. (4), has a clinical feature of white nodular outgrowths on erythematous background mucosa, and for this reason the term erythroleukoplakia is also used (1). The most common sites of involvement include lip commissures (4), buccal mucosa (3)[REMOVED HYPERLINK FIELD] and the soft palate (5). As reported by Feller et al. (6), this form of leukoplakia has a tendency to be more common in patients with tobacco habits; however, there is no statistically significant difference when comparing to idiopathic lesions. On the other hand, Hosni et al. (5) observed history of smoking in all cases of nodular leukoplakia and consumption of alcohol in 54% of them.
Nodular leukoplakia, or a lesion showing nodular features, should be regarded as a dangerous lesion since it is often associated with epithelial dysplasia or carcinoma; it may actually be a cancer during the examination, and it requires detailed microscopic assessment and regular follow-up (2, 4-6).[REMOVED HYPERLINK FIELD] According to Pindborg et al. (4), most of oral lesions with epithelial atypia are clinically nodular leukoplakias. Based on a follow-up study of 248 patients, Pindborg et al. (3) also reported that all nodular leukoplakia developed into a cancer in up to 3.5 years, pointing to the high risk of malignant transformation of this leukoplakia, and to the fact that the transformation runs a rapid course.
A literature search in English (PubMed, Scopus and Web of Knowledge) regarding nodular or speckled leukoplakia associated to malignant transformation retrieved eight papers (2-9), including a large occurrence of nodular leukoplakia on lip commissures and buccal mucosa (3, 4, 7, 8) when compared to other areas affected by this same condition and all revealed a high incidence of epithelial dysplasia and carcinoma.
This case demonstrates an oral squamous cell carcinoma (OSCC) in a lesion diagnosed clinically as nodular leukoplakia, and highlights the importance of a proper selection of the area to be biopsied by a dentist, allowing an accurate final diagnosis.
A 66–year-old Caucasian man, with type 2 diabetes, non-smoker, non-drinker, complained about a cheek lesion with a pinch-like sensation presenting four years of development. During the first examination in another clinic, the patient reported that a white lesion on the right side of the inferior lip had been biopsied two years before, and it recurred. The microscopic diagnosis was chronic stomatitis with lichenoid pattern.
Upon an intra-oral examination, we observed a single, non-indurated, non-removable, extensive area of many white nodule separated by small red areas, located on the inferior lip, right oral commissure, and buccal mucosa. The lesion had irregular shape, with definite borders and clear limits measuring 2cm in length and 1cm in width (Figure 1). No lymphadenopathy was observed.
An incisional biopsy was performed involving a selected area that had both white and red regions in the buccal mucosa. The microscopic analysis revealed oral mucosa lined by hyperparakeratinized and hyperplastic stratified squamous epithelium with papillary surface and elongated rete ridges. In the lower third of the epithelial lining, there were noticeable areas with dysplastic features, such as hyperchromatism, pleomorphism, evident nucleoli, dyskeratosis, basal layer hyperplasia, drop-shaped epithelial ridges and few atypical mitoses. In addition, loss of epithelial architecture in some regions of the lining was present. There were also Munro microabscesses, particularly in the upper layers of the epithelium, and microbial biofilm at the surface (Figure 2). To better detect fungal colonization, the Periodic acid-Schiff (PAS) staining was performed and candidal hyphae were found, mainly in the superficial layers of the epithelium. In the lamina propria, there were a few islands of epithelial cells of various sizes, suggestive of microinvasion, surrounded by intense mononuclear inflammatory infiltrate, making the identification of dysplastic aspects difficult (Figure 2). The subepithelial region also had intense band-like mononuclear inflammatory infiltrate, resulting in the degeneration of the basal cell layer with Civatte body formation.
Based on the clinical history and microscopic features of the lesion, the diagnosis of nodular leukoplakia with a focus of possible malignant transformation was suggested, but this was not conclusive since there was the possibility of a pseudoepitheliomatous hyperplasia rather than malignant transformation. Therefore, one month later, a second incisional biopsy was taken on the buccal mucosa at three different areas of the lesion (indicated by circles in Figure 1) and the morphological features presented in only one of the sections were consistent with invasive OSCC (Figure 3).
The patient was referred to a Cancer Hospital and the lesion was totally excised. The microscopic diagnosis of this biopsy was OSCC. The patient is under a 2-year follow-up and no recurrence has been reported.
This case demonstrates an early OSCC that occurred at a nodular leukoplakia. According to the reported history, we believe that this was a case of nodular leukoplakia from the beginning, which has undergone malignant transformation, since the patient reports that the current lesion occurred in the same location as the previously biopsied lesion; and according to the patient representing a recurrence. Also, we consider it to be a recent transformation, since we observed microscopically focal areas of malignant invasion; i.e. from three areas selected for incisional biopsy, only one of them showed morphological alterations compatible with OSCC. However, we cannot accurately determine whether the OSCC developed de novo, presenting features of nodular leukoplakia, or from preexisting leukoplakia.
Based on our clinical examination, the lesion was a nodular leukoplakia, with features of potentially malignant lesion but not necessarily malignant. Thus, one of the most important points that we want to emphasize here is the importance of choosing the critical area(s) to perform incisional biopsy, in the case of a potentially malignant lesion from a clinical standpoint. The difficulty in managing patients with potentially malignant oral lesions is deciding which mucosal lesions or areas will progress to OSCC. Hosni et al (5) found dysplasia to invasive OSCC in all the erythroplastic areas of nodular leukoplakias. This finding highlights the need for taking biopsies of various areas in cases of nodular leukoplakia, including mainly the erythroplastic component.
In our case report, after a direct and effective communication between the dentist and oral pathologist, we decided to perform a second incisional biopsy in order to achieve an accurate microscopic diagnosis regarding tumor invasion, and also to guide the best patient outcome. The reason for the difficulty in microscopic diagnosis based on first biopsy was the possibility of it being a pseudoepitheliomatous hyperplasia rather than a real tumor invasion. Besides, the dysplastic features were restricted to the lower third of the epithelial lining, and there were a few small islands of epithelial cells in the lamina propria but without an evident dysplasia. As a consequence of interdisciplinarity, we believe that the diagnosis of malignancy was early. Hence, the patient showed no recurrences in a follow-up of two years.
The presence of Candida has been observed in the majority of cases of nodular leukoplakia by means of microbiological and histological analysis (3, 5, 10), which corroborates our case, which presented extensive fungal colonization in the surface of epithelial lining as well as microabscesses of Munro. Besides, the presence of Candida and epithelial dysplasia is higher in multiple oral leukoplakia than in single oral leukoplakia (11). Some studies demonstrated that Candida invasion within the oral mucosa may induce an hyperplastic reaction that is a protective response of the host (12) and have an important association with moderate and severe epithelial dysplasia (13). According to Chiu et al. (11), nitrosamine compounds produced by Candida species may directly, or in concert with other chemical carcinogens, activate speciﬁc proto-oncogenes and thus initiate the development of malignant lesions. Thus, following this line of reasoning, the fungal superinfection could be considered a significant risk factor for oncogenesis (14). However, it is still very controversial whether the Candida species are involved in the etiology or progression of leukoplakia (15) requiring additional studies for a better understanding. In conclusion, in our case report, there remains an unresolved question whether epithelial dysplasia developed from an infected nodular leukoplakia due to the carcinogenic potential of the fungus or if the Candida infection was due to irregular verrucous surface of leukoplakia that provides niches for colonization, having no participation in the occurrence of dysplasia.
Regardless, the clinically homogeneous leukoplakia associated with a Candida albicans infection may change and become ulcerated or have a more erythematous appearance. Such a lesion may eventually develop into a nodular leukoplakia (1).[REMOVED HYPERLINK FIELD] The use of antifungals has been indicated for nodular leukoplakia; although the lesion does not disappear on eradication of this surface mycosis, eliminating the fungus may change the clinical aspect of non-homogeneous such as nodular to the homogeneous type of leukoplakia (1, 3, 10, 15).
Although our case report showed no evidence of koilocytes, we cannot rule out the possibility of an association of human papillomavirus (HPV) with the lesion due to hyperplastic epithelium and absence of tobacco history. The HPV, especially the type 16, has been found in more than 80% of oral leukoplakias, irrespective of the degree of epithelial dysplasia (16), and in 50% of oropharyngeal squamous cell carcinoma (17). On the other hand, the HPV infection has been encountered in 12.5% of the nodular leukoplakias, demonstrating lower HPV prevalence than in other types of leukoplakia (18).
Finally, the present case reinforces the importance of a proper selection of the area to be biopsied in clinically non-homogeneous leukoplakias, and a close collaboration between a dentist and oral pathologist to establish an accurate diagnosis.