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.