Langerhans cell histiocytosis (LCH) is a disorder of the mononuclear phagocyte system that can affect almost any organ and system. The most common central nervous system (CNS) manifestation in LCH is the infiltration of the hypothalamic-pituitary region leading to destruction and neurodegeneration of CNS tissue. The latter causes the most frequent endocrinological manifestation, that is, central diabetes insipidus (CDI), and less often anterior pituitary hormone deficiency (APD). The reported incidence of CDI is estimated between 11.5 and 24% and is considered a risk factor for neurodegenerative disease and APD. Three risk factors for development of CDI are recognized in the majority of the studies: (1) multisystem disease, (2) the occurrence of reactivations or active disease for a prolonged period, and (3) the presence of craniofacial bone lesions. Since CDI may occur as the first manifestation of LCH, differential diagnosis of malignant diseases like germ cell tumours must be made. APD is almost always associated with CDI and can appear several years after the diagnosis of CDI. Growth hormone is the most commonly affected anterior pituitary hormone. Despite significant advances in the knowledge of LCH in recent years, little progress has been made in preventing long-term sequelae such as those affecting the hypothalamic-pituitary system.

The abstract of this research has been submitted to the virtual 36th Annual Meeting of the Histiocyte Society (October and November 2020) titled "High prevalence of BRAFV600E in patients with cholestasis, sclerosing cholangitis, or liver fibrosis secondary to Langerhans cell histiocytosis" and was published in the Pediatric Blood & Cancer journal, and the manuscript has been previously submitted to this journal as a Research Article.

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Pleuropulmonary synovial sarcoma (PPSS) is a primary malignancy of the lung, uncommon in pediatrics (prevalence: 0.1-0.5%) that predominantly affects adolescents and young adults. Overall survival has been reported to be close to 30% at 5 years.Here we report the case of a previously healthy 12-year-old male patient who presented with cough, chest pain, and dyspnea of sudden onset as initial manifestation of left pneumothorax, which persisted after 4 days and required surgical resection of pulmonary bullous lesion. A histological diagnosis of pleuropulmonary synovial sarcoma was made and confirmed by molecular study, which showed chromosomal translocation between chromosomes X and 18: t(X;18) (p11.2;q11.2) in the surgical specimen removed.In patients with persistent or recurrent pneumothorax, it is important to rule out secondary causes, including pleuropulmonary synovial sarcoma. Such poor prognosis determines the need for early diagnosis and aggressive treatment.

Background Cooperative clinical trials has increased the knowledge on pediatric tumors, however, this is not the case for rare tumors (RT). Objective To describe the incidence, clinical characteristics and outcome of RT in the pediatric age diagnosed at Garrahan Hospital. Material and methods Retrospective descriptive study of patients (pts) between 0 and 18 years admitted between January 2 007 and December 2 017, with diagnosis of RT. Results Of 1 657 pts with diagnosis of solid tumors, 164pts (9.9%) corresponded to RT, 71.95% (118pts) were under 14 years old and 81.7% (130pts) were male. In order offrequency RT were: thyroid carcinoma (ca) 60pts, adrenal ca 14pts, lung tumors 14pts, melanoma 13pts, salivary glands ca 11pts, gastrointestinal tumors 8pts, non-gonadal germinal tumors 7pts, pancreatic tumors 7pts, renal ca 6pts, nasopharyngeal ca 5pts, pheochromocytoma/paraganglioma 5pts, timo 1pte. The treatment received depended on the type of tumor and stage. With a median follow-up of 34.9 months (range: 1-128.5 months), 133pts (78.7%) are alive and only 10pts (6%) were lost to follow-up. Conclusion Knowing these initial data will allow us to propose new registration strategies and to develop multidisciplinary proposals for diagnosis, treatment and follow-up.