A Study of Panobinostat in Pediatric Patients With Solid Tumors Including MRT/ATRT

Inclusion Criteria: * Patients must be \< 40 years of age. * Patient must have been histologically diagnosed with osteosarcoma, neuroblastoma or MRT/ATRT at time of diagnosis or relapse. \[osteosarcoma and neuroblastoma arms are closed to recruitment\]. * Patient disease is refractory to conventional therapy, in the case of osteosarcoma, neuroblastoma and MRT/ATRT or there is an absence of effective conventional therapy available in the case of ATRT. Patients must have stable disease (SD) or better following treatment with salvage therapy. * Karnofsky performance level greater than or equal to 60% for patients 16 years of age and greater, OR Lansky performance levels greater than or equal to 60% for patients less than 16 years of age. * Life expectancy of greater than 8 weeks. * Fully recovered from acute toxic effects of all prior chemotherapy, immunotherapy or radiotherapy prior to entering study. * Patients with CNS tumours who are receiving dexamethasone are on a stable/decreasing dose for at least 1 week. * Adequate BM function * Adequate renal function * Adequate liver function * Adequate cardiac function * Adequate pulmonary function * Adequate CNS function - seizure free for at least 2 months * Adequate serum calcium, magnesium and potassium concentrations * If female and post-menarchal, pregnancy test must be negative. * If of reproductive potential, have agreed to use effective contraceptive method. * If female and lactating, have agreed not to breastfeed. * Patient and/or their legal guardian have signed a written informed consent form. Exclusion Criteria: * Have received myelosuppressive chemotherapy and/or biologic therapy within 3 weeks (4 weeks if prior nitrosourea). * Have received local palliative radiotherapy within 2 weeks. * Have received craniospinal radiotherapy within 3 weeks. * Have received greater than or equal to 50% radiation of the pelvis within 6 weeks. * Have received other substantial BM radiation within 6 weeks. * Have received growth factor(s) within 1 week. * Are receiving enzyme inducing anticonvulsant therapy. * Are receiving medications associated with prolongation of QTc interval * Are receiving hydrochlorothiazide. * Are receiving metronidazole and/or disulfiram * Have uncontrolled sepsis. * Have previously received panobinostat. * Have symptoms of congestive heart failure, uncontrolled cardiac rhythm disturbance, or a QTc greater than or equal to 450msec.