Background: The diagnosis of oral lichenoid lesions (OLL) remains a challenge for clinicians and pathologists. Although, in many cases, OLL cannot be clinically and histopathologically distinguishable from oral lichen planus (OLP), one important difference between these lesions is that OLL has an identifiable etiological factor, e.g. medication, restorative material, and food allergy. The list of drugs that can cause OLL is extensive and includes anti-inflammatory drugs, anticonvulsants, antihypertensives, antivirals, antibiotics, chemotherapeutics, among others. This work aimed to perform a literature review of OLL related to chemotherapy drugs and to report two cases of possible OLL in patients with B-cell and T-cell non-Hodgkin lymphomas in use of chemotherapy and adjuvant medications. We also discuss the challenge to clinically and histopathologically differentiate OLL and OLP. Case presentation: In both cases, oral lesions presented reticular, atrophic, erosive/ulcerated, and plaque patterns. The diagnosis of OLL was initially established in both cases by the association of histopathology and history of onset of lesions after the use of medications. Although the patients have presented a significant improvement in the oral clinical picture for more than 2 years of follow-up, they still have some lesions. Conclusion: A well-detailed anamnesis associated with the drug history, temporal relationship of the appearance of the lesions, and follow-up of patients are fundamental for the diagnosis of OLL related to drugs. Nevertheless, its differentiation from OLP is still a challenge.

Assessment of oral epithelial dysplasia is the gold standard for investigating the risk of malignant progression. The World Health Organization (WHO) methods and the binary system have limitations. This study assess the inter- and intra-observer variability of the architectural and cytological criteria and the classification of the presence and degree of epithelial dysplasia in oral lichen planus (OLP) and oral lichenoid lesion (OLL), using both the 2017 WHO criteria and the binary system. The sample consisted of 65 biopsies from lesions classified as OLP and OLL according to the American Academy of Oral and Maxillofacial Pathology (AAOMP) criteria. The histological slides were reevaluated by two oral pathologists. The individual alterations with most inter-observer disagreement were atypical mitotic figures (43.1%), loss of cohesion between epithelial cells (38.5%) and drop shape rete ridges ridges (38.5%). Inter-observer agreement analysis did not show statistically significant agreement regarding the classification of epithelial dysplasia grade by WHO criteria, only regarding the binary system classification (k=0.257; p=0.035). Intra-observer agreement analysis by evaluator 1 showed that the classification of epithelial dysplasia grade according to both methods had statistically significant agreement (k=0.546; p=0.004, k=0.861; p<0.001). Considering evaluator 2, only the evaluation of the WHO system classification showed statistically significant agreement (k=0.593; p=0.010). The evaluation of epithelial dysplasia is subjective and focal changes and inflammatory infiltrate, characteristic of OLP and OLL, can increase the degree of disagreement among evaluators. The binary system presents better inter-observer agreement, while the WHO system presents better intra-observer agreement. Key words:Oral lichen planus, oral lichenoid lesion, oral lichenoid disease, dysplasia, inter-observer variation.

The most common oral choristomas are consisted of thyroid tissue and bone. The presence of sebaceous glands in the oral mucosa, especially in the buccal mucosa and labial mucosa, is often considered a normal anatomical variation since they are observed in about 80% of the population and are called ectopic sebaceous glands or Fordyce's granules. However, the presence of these glands on the tongue is rare, with only 11 cases in the dorsum of the tongue reported in the English literature, and it is considered a choristoma. This paper aims to report the third case in the literature of a congenital sebaceous choristoma on the tongue. An 11-year-old white male patient presented a firm sessile papule, without color alteration, measuring 0.4 cm x 0.3 cm in diameter, in the middle third of the dorsum of the tongue with a slight increased size in the last months. Histopathological examination showed an invagination of the epithelium into the connective tissue, forming a ductal structure covered by stratified squamous epithelium. The deeper areas had normal well-differentiated sebaceous glands, with ducts connected to the central duct. Considering clinical and histopathological findings the diagnosis was sebaceous choristoma. Despite being rare, sebaceous choristomas should also be considered in the differential diagnosis of tongue abnormalities or lesions. Although the pathogenesis is not well understood, the present report, as a congenital choristoma case in the midline, reinforces the hypothesis of a disorder with embryological origin and a possible relationship with thyroglossal duct remnants. Key words:Choristoma, Oral Mucosa, Tongue.