title: A rhabdomyoma within a multilocular thymic cyst in a p53-null mouse.
abstract: A 9-month-old p53-null female mouse was found dead in its cage. At necropsy, a large thymic mass encompassed the heart. Microscopically, the mass was composed of numerous varying-sized cysts lined with simple squamous epithelial cells to columnar ciliated cells. Also present within this mass was a large aggregate of loosely arranged fusiform-shaped cells. These cells also were found in smaller numbers in the connective tissue surrounding the cysts. The larger aggregate of fusiform cells was positive for desmin and S-100 and negative for smooth muscle actin. Electron microscopy revealed well-formed Z lines and I bands of skeletal muscle phenotype. A diagnosis of rhabdomyoma within a congenital multilocular thymic cyst was made. The thymus contains a small population of myoid cells, which should be taken in consideration when evaluating thymic tumors.
authors.affiliation: Division of Veterinary Resources, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA. starostm@mail.nih.gov
authors.forename: M F
authors.initials: MF
authors.lastname: Starost
authors.forename: K
authors.initials: K
authors.lastname: Tsang
authors.forename: P M
authors.initials: PM
authors.lastname: Zerfas
authors.forename: C A
authors.initials: CA
authors.lastname: Stratakis
mesh_terms: D000818:Animals; D005260:Female; D016158:Genes, p53; D008476:Mediastinal Cyst / Q000473:pathology / Q000662:veterinary*; D008479:Mediastinal Neoplasms / Q000473:pathology / Q000662:veterinary*; D051379:Mice; D018345:Mice, Knockout / Q000235:genetics; D012207:Rhabdomyoma / Q000473:pathology / Q000662:veterinary*; D012376:Rodent Diseases / Q000235:genetics / Q000473:pathology*; D013950:Thymus Gland / Q000473:pathology