With an annual cumulative occurrence of approximately 15,000 in North America, all childhood cancers are rare. Very rare cancers as defined by both the European Cooperative Study Group for Rare Pediatric Cancers (EXPeRT) and the Children’s Oncology Group (COG) fall into two principal categories: those so uncommon (fewer than 2 cases/million) that their study is challenging even through cooperative group efforts (e.g. pleuropulmonary blastoma, desmoplastic small round cell tumor) and those that are far more common in adults and therefore rarely studied in children (e.g. thyroid, melanoma, gastrointestinal stromal tumor). [1](#ref-0001) Treatment strategies for these latter tumors are typically based on adult guidelines, although the pediatric variants of these tumors may harbor different genetic signatures and demonstrate different behavior. If melanoma and differentiated thyroid cancer are excluded, other rare cancer types account for only 2% of the cancers in children aged 0 to 14.[1](#ref-0001) This article highlights several of the most common rare tumor types.