Families of children with rare diseases (i.e., not more than 5 out of 10.000 people are affected) are often highly burdened with fears, insecurities and concerns regarding the affected child and his/her siblings. The aim of the present research project is to examine the psychosocial burden of the children with rare solid abdominal tumors and their family in order to draw attention to a possible psychosocial care gap in this population.

The central objective of the cross-sectional study is to show the psychosocial supply gap for families with children and adolescents affected by rare diseases in the field of oncology pediatric surgery. Among the rare diseases that are included are rare solid abdominal tumors. In order to have a comparative sample, additional data of a matched control group are collected. Central standardized psychosocial outcomes will be assessed from the perspectives of the parents and the affected child.

Inclusion Criteria (families of rare disease):

• Family with at least one child between 0 and 17 years with rare solid abdominal tumors.
• Consent to participate in the study.
• Sufficient knowledge of the German language of parents and children.

Exclusion Criteria (families of rare disease):

- Severe acute physical, mental and/or cognitive impairment of the child, so that the questionnaire survey does not appear possible and/or unreasonable at this stage.

Inclusion Criteria (control group):

• Family with at least one child between 0 and 17 years who have undergone a surgical procedure in the first 3 years of life that does not cause chronic complaints
• Consent to participate in the study.
• Sufficient knowledge of the German language of parents and children.

Exclusion Criteria (control group):

- Families of children with a congenital or chronic disease.

Clinical study participants for the diagnostic study are patients who have sought treatment at the University Medical Center Hamburg-Eppendorf and University Medical Center Mannheim due to a rare pediatric disease. Participants in the healthy control sample are matched to the clinical sample in terms of age and gender. Included are families of children aged 0-17 years, who have undergone a surgical procedure at the University Medical Center Hamburg-Eppendorfin and University Medical Center Mannheim the first 3 years of life that does not cause chronic complaints; such as hernia surgery or testicular relocation.