With exception of hotspot mutations found in DICER1, we found only a few mutations in other miRNA biogenesis genes, i.e. DROSHA, DGCR8 and XPO5, which have been recently observed in different childhood cancers associated with DICER1 syndrome and in Wilms' tumor (56–59,66). The gene discussed is XPO5; the disease is childhood malignant neoplasm.