This phase II trial studies how well tazemetostat works in treating patients with solid tumors, non-hodgkin lymphoma, or histiocytic disorders that have spread to other places in the body and have come back or do not respond to treatment and have EZH2, SMARCB1, or SMARCA4 gene mutations. Tazemetostat may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth.