NCIthesaurus orbit rhabdomyosarcoma orbit alveolar rhabdomyosarcoma disease_ontology NCI:C6247 UMLS_CUI:C1335126 DOID:4384 Alveolar Rhabdomyosarcoma of the orbit An orbit rhabdomyosarcoma that is characterized by ill-defined aggregates of poorly differentiated malignant cells that are loosely arranged and separated into irregular ovoid spaces by thin fibrovascular septa in an alveolar pattern which is absent in the solid form.