**10. Spontaneous tumor models in zebrafish**

As it is the case for mice, there are also several genetically engineered spontaneous tumor models available in the zebrafish. While these models may be regarded to more closely model the clinical pathogenesis of cancer, the same limitations are relevant for the zebrafish models as those described for mice, most notably the very heterogeneous tumor onset and growth both for different tumors within each fish but also between different fish.

### **10.1 Peripheral nerve sheath tumors**

Homozygous *tp53M214K* mutant zebrafish which carry a mis-sense mutation in exon 7 of the *P53* gene, giving rise to spontaneous formation of abdominal and periocular tumors at an age of 8-16.5 months. HE staining of ocular and abdominal tumors showed that these tumors are mainly composed of spindle cell and epitheloid cell neoplasms which recapitulate characteristics of human malignant peripheral nerve sheath tumor (MPNST). Intraperitoneal implantation of extracted zMPNST cells into irradiated wild type adult zebrafish led to formation of typical zMPNST tumors after less than one month post transplantation (Berghmans et al, 2005).
