Background: Retinoblastoma (RB) is a relatively uncommon tumour in childhood. The incidence of retinoblastoma in Mexico is probably higher than the incidence reported worldwide, however there is not enough information about the characteristics of this illness in Mexico. This report aims to present the results of a multicentre clinical survey of RB in Mexico. Methods: A retrospective study was carried out on all RB cases treated in 16 institutions during the last six years. The variables analysed were age at diagnosis, sex, affected eyes, treatment modalities, and pathological staging. Overall survival was obtained. Results: The authors analysed 500 cases; age range was 0-182 months. There were 364 unilateral cases (72.8%). Enucleation was performed in 84.9% of the patients. The St Jude's staging was: 7.4% stage I, 52.8% stage II, 18.0% stage III, 11.4% stage IV, 7.2% not evaluated, and 3.2% missing data. Chemotherapy was used in 74.4% of the patients. Disease free survival was 89% at 73 months follow up. Conclusions: The paper presents a great number of cases and pioneers multicentre studies in paediatric ophthalmology and oncology in this country. Given the great number of patients in advanced stages and the variability on treatment schemes, it is evident that it is mandatory to work in a cooperative group and develop a national early detection programme as well as a treatment protocol which include all specialists involved in the care of patients with RB.

The purpose of this study was to determine the prevalence of oral manifestations in pediatric patients with acute lymphoblastic leukemia (ALL) receiving chemotherapy, and to evaluate the significance of independent risk factors (oral health, gender, age, time and type of treatment, and phase of chemotherapy). A crosssectional study was made in 49 children with ALL between 2 and 14 years of age. To describe oral manifestations,a clinical diagnosis was made and the following criteria were applied: the OHI-S index to describe oral health and the IMPA index to describe periodontal conditions and to differentiate gingivitis from periodontitis. The prevalence of oral manifestations was: gingivitis, 91.84%; caries, 81.63%; mucositis,38.77%; periodontitis, 16.32%; cheilitis, 18.36%; recurrent herpes, 12.24%; and primary herpetic gingivostomatitis,2.04%. Other oral manifestations were: dry lips, mucosal pallor, mucosal petechiae, ecchymoses,and induced ulcers. The prevalence of oral candidiasis was 6.12%. It was observed that high risk ALL and poor oral hygiene were important risk factors for the development of candidiasis and gingivitis. The type of leukemia, gender, and phase of chemotherapy were apparently associated with the presence of candidiasis, gingivitis, and periodontitis, and they could be considered risk factors for the development of oral manifestations.

Langerhans cell histiocytosis (LCH), which is a rare granulomatous pediatric disease of unknown etiology, is characterized by the idiopathic proliferation and accumulation of abnormal and clonal Langerhans cells or their marrow precursors, resulting in localized, solitary or multiple destructive lesions. These lesions are most commonly eosinophilic granuloma, which are found in craniofacial bone structures such as the skull and mandible, skin and other organs. In children, the disease has a variable initial presentation, and the clinical course, prognosis and survival are unpredictable. The aims of this report were to present an LCH case in a girl aged 2 years, 8 months and her clinicopathological features, to describe the bucodental management provided, and to discuss special dental considerations of this disease. Key words:Children, dental management, histiocytosis, Langerhans cells.

Overall, 18 patients died due to acute treatment toxicity, resulting in a cumulative incidence of toxic death of 10.84% and an early death rate of 7.23%, defined as <30 days after initial treatment. In conclusion, there is an urgent need to establish an academic collaboration to create strategies to improve pediatric cancer care according to our resources, especially in diseases with expected excellent prognosis as B-NHL. These strategies must include comprehensive supportive care, early referral, and the creation of easy communication between pediatric and adults centers as well as late-effects clinics.