Unusual intraoral cancer with unexpected outcome in a patient with xeroderma pigmentosum: An alert for antineoplastic treatment Mailon Cury Carneiro, Talita de Carvalho Kimura, Elen de Souza Tolentino, DDS, MSc, PhD, Neli Pieralisi, DDS, MSc, PhD, and Vanessa Cristina Veltrini, DDS, MSc, PhD Xeroderma pigmentosum (XP) is a rare autosomal disorder characterized by extreme sensitivity to ultraviolet radiation. DNA repair mechanisms are impaired, and minimal sun exposure can lead to the development of cutaneous neoplasms in very young patients. Intraoral carcinomas are uncommon and, when present, are located mainly at the tongue tip. We report an unprece- dented case of squamous cell carcinoma (SCC) in the floor of mouth of a 23-year-old woman with XP. The patient was referred to the oncologist, and 2 months after surgical resection, she underwent a single session of chemotherapy plus radiotherapy. How- ever, she died 73 hours after undergoing her first chemotherapy session. Considering the unexpected outcome of this case, we also investigated possible exacerbated adverse effects of antineoplastic treatments (especially cisplatin-based chemotherapy) in patients with XP and reviewed the main characteristics of the disease, especially cases with oral manifestations reported in the lit- erature. (Oral Surg Oral Med Oral Pathol Oral Radiol 2020;129:e1 e11) Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder, in which DNA damages are difficult to repair, and the disorder is mainly caused by the ultra- violet (UV) radiation. 1 In the very first decades of life, patients develop numerous malignant skin neo- plasms. 1,2 The skin on both the head and the neck is generally affected, and patients have a higher risk of developing lower lip and tongue tip cancer (areas most exposed to UV radiation). Moreover, these patients have a 10 to 20 times higher risk of developing inner neoplasms that do not have a UV etiology, suggesting that the repair of the oxidative damage to the endoge- nous DNA could also be deregulated. 3 The disease has a severe course, and about two- thirds of patients are unaware of their own condition and/or do not apply preventive measures. 3 Early diag- nosis is very important to prevent malignant complica- tions, which are the main causes of death. In addition, the literature speculates on possible exacerbation of adverse effects when certain antineoplastic drugs, such as cisplatin, are used in these patients. 4 Considering that intraoral lesions are uncommon, the aim of this report is to describe a case of squamous cell carcinoma (SCC) on the floor of the mouth of a 23-year-old woman with XP, whose response to treatment pro- gressed in a severe and unexpected way. In addition, the oral manifestations of XP reported in the literature, as well as the influence of antineoplastic treatment on the clinical course of the disease, are analyzed. CASE REPORT A 23-year-old woman with a previous diagnosis of XP was referred to the UEM Dental School with a com- plaint of “macula and sore in the mouth”, of 8 months’ of evolution. She had a family history of consanguine- ous marriage of parents and a brother with XP, who underwent lower lip resection. Both the patient and her brother had been diagnosed with XP in their childhood. She denied neurologic disturbances and prior surgical procedures. Weak photophobia and numerous hyper- pigmented ephelides throughout the body were observed, as well as a melanocytic nevus in the region of the right eyebrow (Figure 1). No lymphadenopathy was observed. Intraoral examination revealed a painless endophytic ulcer on the floor of the mouth, with a hardened base and yellowish-white borders, measuring approximately 2 cm (Figure 2A). In addition, a 4-cm verrucous white plaque was present at the tip and borders of the tongue, with diffuse limits and focal area of erythema and ulceration (Figure 2B). On the basis of the clinical findings, presumptive diagnoses of SCC in the floor of the mouth and leu- koplakia or erythroleukoplakia in the tongue were hypothesized. Incisional biopsy of the lesion fol- lowed by histopathologic examination showed neo- plastic parakeratinized squamous epithelium, with extensive connective tissue infiltration. The muscu- lar plane was also involved. Numerous dyskeratotic foci indicating loss of stratification were seen, and in neoplastic nests, malignant epithelial cells exhib- ited pleomorphism, hyperchromatism, and atypical mitoses (Figure 3), confirming the diagnosis of SCC. In the tongue lesion, a hyperorthokeratinized stratified squamous epithelium with associated hypergranulosis was present. In the lower layers, pleomorphism, hyperchromatism, and areas of Department of Dentistry, State University of Maringa, Maringa, PR, Brazil. Received for publication May 22, 2019; returned for revision Sep 3, 2019; accepted for publication Sep 28, 2019. Ó 2019 Elsevier Inc. All rights reserved. 2212-4403/$-see front matter https://doi.org/10.1016/j.oooo.2019.09.017 e1 Vol. 129 No. 1 January 2020