 HSV1716, an oncolytic virus, is a mutant herpes simplex virus HSV type I, deleted in the RL1 gene which encodes the protein ICP34.5, a specific determinant of virulence. Mutants lacking the RL1 gene are capable of replication in actively dividing cells but not in terminally differentiated cells - a phenotype exploited to selectively kill tumor cells. In previous clinical studies, HSV1716 has been shown to be safe when injected at doses up to 105 plaque forming units pfu directly into human high-grade glioma and into normal brain adjacent to tumour, following excision of high-grade glioma. In an extension study, HSV1716 has been shown to be safe when injected at a dose of up to 106 pfu directly into brain tumours. Replication of HSV1716 in human glioblastoma in situ has been demonstrated. Following a single administration of HSV1716 by direct injection into active recurrent tumor or brain adjacent to tumor, some patients have lived longer than might have been expected. This study seeks to evaluate the safety of a single injection of HSV1716 in the treatment of extracranial solid tumors in adolescents and young adults. 