Pleomorphic (anaplastic) neuroblastoma in nude mice. Two pleomorphic (anaplastic) neuroblastomas, from two children aged 1 and 6 years, were transplanted into nude mice. Two noteworthy observations were made. In one case, the transplanted tumor gave rise to a soft-tissue sarcoma. Moreover, in both cases hepatic metastases were associated with a striking modification of murine hepatocytes, resulting in hyperchromatic and dysplastic nuclei. The latter finding was particularly evident in the hepatic areas surrounding all metastases of pleomorphic (anaplastic) neuroblastoma cells. 