Oral potentially malignant disorders (OPMDs) are associated with an increased risk of occurrence of cancers of the lip or oral cavity. This paper presents an updated report on the nomenclature and the classification of OPMDs, based predominantly on their clinical features, following discussions by an expert group at a workshop held by the World Health Organization (WHO) Collaborating Centre for Oral Cancer in the UK. The first workshop held in London in 2005 considered a wide spectrum of disorders under the term "potentially malignant disorders of the oral mucosa" (PMD) (now referred to as oral potentially malignant disorders: OPMD) including leukoplakia, erythroplakia, proliferative verrucous leukoplakia, oral lichen planus, oral submucous fibrosis, palatal lesions in reverse smokers, lupus erythematosus, epidermolysis bullosa, and dyskeratosis congenita. Any new evidence published in the intervening Medical Sciences,

These findings differ from those observed in other odontogenic lesions, such as ameloblastic fibroma, odontogenic myxoma, odontogenic fibroma, and hyperplastic dental follicles. The term primordial odontogenic tumour is proposed to describe this novel lesion.

There is currently increasing concern about the relation between microbial infections and cancer. More and more studies support the view that there is an association, above all, when the causal agents are bacteria or viruses. This review adds to this, summarizing evidence that the opportunistic fungus Candida albicans increases the risk of carcinogenesis and metastasis. Until recent years, Candida spp. had fundamentally been linked to cancerous processes as it is an opportunist pathogen that takes advantage of the immunosuppressed state of patients particularly due to chemotherapy. In contrast, the most recent findings demonstrate that C. albicans is capable of promoting cancer by several mechanisms, as described in the review: production of carcinogenic byproducts, triggering of inflammation, induction of Th17 response and molecular mimicry. We underline the need not only to control this type of infection during cancer treatment, especially given the major role of this yeast species in nosocomial infections, but also to find new therapeutic approaches to avoid the pro-tumor effect of this fungal species.

Oral leukoplakia (OL) is the most frequently encountered and emblematic oral potentially malignant disorder (OPMD). Since its first description, OL has received multiple definitions and it is customarily described as "a white plaque with a questionable risk of cancer that can only be diagnosed once other specific conditions have been ruled out" (Reibel et al., 2017;Warnakulasuriya et al., 2007). Classically, OL is more common among adult males consuming tobacco and/or alcohol, or betel quid, with or without tobacco (particularly among Asian populations) and it encompasses two clinical subtypes, homogeneous oral leukoplakia (HOL) and non-homogeneous oral leukoplakia (NHOL) (van der Waal, 2019;Warnakulasuriya et al., 2020).The most important biological element of OL has to do with its malignant potential. The malignant transformation (MT) proportions in reported studies are highly variable (0.13%-34.0%) (Warnakulasuriya & Ariyawardana, 2016). Unfortunately, to date there are no pathognomonic factors or specific data that enable us to accurately predict which OLs from a cohort may suffer malignant transformation (Diz et al., 2011;van der Waal, 2014). A systematic review carried out by Warnakulasuriya &Ariyawardana in 2016 reported that advance age, female gender,

Candida albicans isolated from potentially carcinogenic oral diseases can produce mutagenic amounts of acetaldehyde. Cigarette smoking and alcohol consumption may favour adaptational changes resulting in the upregulation of candidal acetaldehyde metabolism.

A study was made of the oral manifestations in 396 patients with human immunodeficiency virus (HIV) infection. The following risk groups were established: intravenous drug users (79.5%), homosexuals (7.8%), homosexual intravenous drug users (3.3%), heterosexuals (8.1%) and hemophiliacs/transfusion patients (1.3%). The oral lesions, in decreasing order of frequency, were: periodontal disease (78.28%), candidiasis (65.65%), hairy leukoplakia (16.16%), herpes simplex virus lesions (5.30%). Kaposi's sarcoma (2.27%), recurrent aphthous ulceration (RAS) (1.01%), lichen planus (0.5%), non-Hodgkin's lymphoma (0.25%), tuberculous lesion of the tongue (0.25%) and ulcerations of uncertain etiology (0.25%). Attention is drawn to the greater predominance of these lesions in patients with CD4 values of less than 200/ mm3, compared with those who have higher lymphocyte counts.

Schwannoma or neurilemmoma is an infrequent benign tumor in the oral cavity that originates from the Schwann cells on the neural sheath of the peripheral nerves. Schwannomas are frequently located in the soft tissues of head and neck region, but only a 1 to 12% of them are located in the oral cavity. Some histological variants of schwannoma have been described including the cellular, plexiform, epithelioid, ancient, and melanocytic types. The “ancient schwannoma” is an uncommon variant of this tumor that shows specific histological characteristics, and is rare in the oral cavity with less than 15 cases described on the literature. Most of them were located in the tongue or in the floor of the mouth, being the hard palate an extremely rare localization. We present a new clinical case of an ancient schwannoma with a long time of evolution, arising from the nasopalatine nerve, and located in the hard palate of a 35 year old female. We also review the main clinical and histological characteristics of this pathology. Key words:Ancient schwannoma, neurilemmoma, palate, schwannoma.

Candida species (spp) are commensal yeast that can only instigate oral infection (oral candidosis - OC) when there is an underlying predisposing condition in the host. We investigated four controversial topics on OC: (i) How can a microbiological determination of OC be made as Candida spp. are commensal yeasts and not all of them form hyphae or pseudohyphae during infection? (ii) Is median rhomboid glossitis (MRG) a manifestation of candidal infection? (iii) Can candidal infection cause palate papillary hyperplasia (PPH)? (iv) What is the best therapeutic treatment for denture-associated erythematous stomatitis (DAES)? Results from extensive literature searches, including a systematic review, suggested the following: (i) the diagnosis of OC merely on the basis of the presence of yeasts is an oversimplification of a complex process. No convincing evidence of a single test or method better able to discriminate the transition from candidal saprophytism to pathogenicity has been reported in the literature; (ii-iii) conclusive evidence of a direct aetiopathogenic relationship between MRG and PPH and candidal infection has not been found; and (iv) only limited evidence is available for any DAES treatment, thus making it impossible to make strong therapeutic recommendations.