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Olfactory neuroblastoma (ON) is a rare tumor commonly presenting between 50 and 60 years of age. In pediatric age this tumor is even rarer, with an estimated incidence of 0.1 per 100,000 children up to 15 years. It arises from the olfactory neurorepithelium of the nasal cavity, and it can be locally aggressive, spreading to the orbital cavity, skull base, intracranial cavity. In rarer cases it can also give distant metastasis, more frequently to regional lymph nodes and less commonly to distant sites like liver, lungs and bones. Prognosis varies depending on the stage at presentation (including dural invasion, regional nodal involvement, and distant metastasis), the histological grade, and aspects related to the treatment, such as the possibility to achieve clear margins with surgery and the multimodal approach. Chemotherapy, surgery and radiotherapy have been used to treat these patients and the different approaches have been reported in the literature. Given the rarity of the disease no shared guidelines exist for the management of this entity in children, but some suggestions can be given to optimize the ON management.This study presents the internationally recognized recommendations for the diagnosis and treatment of ON in children and adolescents, established by the European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT) group within the EU-funded project Pediatric Rare Tumors Network - European Registry (PARTNER).

Melanotic neuroectodermal tumor of infancy (MNTI) is a very rare benign neoplasm of probable neurocristic origin. It primarily affects children in the first year of life, with the median age at diagnosis of 4.5 months (range 0–804 months). It usually presents as a fast-growing, painless tumor developing within maxilla, skull bones or mandible but other locations are also possible, especially in older children. The cornerstone of treatment of MNTI is surgery, however local relapses after incomplete tumor excision are common, particularly in patients younger than 2 months of age. Rare cases of multiple recurrent, inoperable or metastatic MNTI pose therapeutic challenges. In such clinical scenarios, various regimens of neoadjuvant chemotherapy based on schemes for neuroblastoma or Ewing sarcoma have been used with partial regressions in some patients, enabling less mutilating delayed surgery. The use of radiotherapy is limited due to very young age of patients with MNTI. No targeted therapies have been found useful so far. Long-term prognosis of localized MNTI is favorable. However, extensive or recurrent lesions can result in functional or esthetic sequelae after surgical removal. Rare cases of malignant/metastatic tumors and MNTI diagnosed in older children have unfavorable outcomes. Further collaborative studies to establish standards of management in patients with MNTI are necessary to improve outcomes and diminish sequelae of surgery. This article presents a literature review on this very rare tumor entity, re-evaluated in the light of the experience gained in the national working groups joined together within the European Cooperative Study Group in Pediatric Rare Tumors (EXPeRT).

Background: Very rare tumors (VRTs) in children and adolescents are orphan diseases defined by an annual incidence of

Very rare tumors (VRTs) in pediatric age represent many different diseases. They present an annual incidence

Germline predisposing pathogenic variants (GPVs) are present in approximately 8–10 % of children with all cancer types. Very rare tumours (VRTs) represent many different diseases, defined with an annual incidence

Very rare cancers in children and adolescents pose a unique challenge for optimal care and research. Due to their rarity and diversity, there is a lack of standardized treatments and limited data to guide clinical decision-making. This paper aims to provide solutions for addressing these challenges through a multidisciplinary approach involving clinicians, researchers, and patient advocates. In recent years, members of the European Cooperative Study Group for Paediatric Rare Tumors (EXPeRT) and members of the European Society of Pediatric Oncology (SIOPE) clinical council worked within the EU Joint Action on Rare Cancers (JARC) and the Paed Can European Reference Network (ERN) on solutions to improve the care and research in the field. This includes a better classification, more financial resources, higher awareness and support by stakeholders, an international database, as well as harmonized diagnostic and therapeutic guidelines. Further research projects in the field of molecular biology, a better collaboration between medical oncologists and pediatricians, and a general strategy to facilitate access to modern therapies are urgently needed.

Background: Salivary gland carcinomas (SGCs) are exceedingly rare in children, with a reported annual incidence of 0.8–1.4/1000,000 under 20 years of age. Evidence regarding optimal treatment of pediatric SGCs is limited, and for a long time, no guidelines have been available. Here, we report on an international retrospective series of SGCs in children and adolescents collected by several national rare tumor study groups cooperating in the European Cooperative Study Group of Pediatric Rare Tumors (EXPeRT) Patients and methods: Patients diagnosed between 2000 and 2014 were included. Data were reviewed by the respective national rare tumor working groups and reported on a harmonized data sheet to EXPeRT for central analysis. Results: Overall, 121 patients were identified, including 103 patients with parotid tumors, 12 with submandibular tumors and six tumors in minor glands. In 11 patients, SGCs were secondary cancers. Mucoepidermoid carcinoma was the most frequent diagnosis (n = 65), followed by acinic cell carcinoma (n = 39), adenocystic carcinoma (n = 7), sialoblastoma (n = 3) and other carcinomas (n = 7). All patients underwent tumor resection (R0: 66%, R1: 34%). Neck dissection was performed in 47 patients, revealing nodal metastases in 13. Twenty-four patients underwent irradiation, and 11 patients received adjuvant chemotherapy. During a median follow-up of 25 (6–140 months), 14 relapses were observed (7 local, 5 with nodal and 2 with distant metastases). Five patients died of disease. Higher histological tumor grade was associated with advanced local tumor stage and risk of recurrence. Conclusions: SGCs in children and adolescents mostly present as localized tumors with low malignant potential. In approximately 10% of patients, regional lymph node metastases present at diagnosis. After complete resection, prognosis is favorable. Surgery is the mainstay of treatment; adjuvant local or cervical irradiation should be reserved to those rare patients with nodal metastases or less favorable biology such as adenocystic carcinoma.