title: Diagnosis of thymolipoma with fine needle aspiration biopsy. Report of a case initially misdiagnosed as liposarcoma.
abstract: BACKGROUND
  Thymolipomas are the most outstanding mesenchymal mediastinal tumors although they represent only a small percentage of thymic neoplasms. Their histogenesis remains unsolved, and they are usually benign. Fine needle aspiration biopsy (FNAB) has become the method of choice for the study of mediastinal tumors, including thymolipomas. Making the correct diagnosis depends on the availability of all thymic and lipomatous components as well as on the correct application of a differential diagnosis with other lipomatous tumors.
  
  
  METHODS
  A 24-year-old woman had a 3-month history of coughing with sputum, fever, asthenia, adynamia, headaches and anemia. Physical examination revealed a bilateral pulmonary condensation syndrome. Imaging studies showed a well-defined, large mass occupying both hemithoraxes and the mediastinum. FNAB revealed an admixture of atypical adipocytes, nonneoplasic lymphoid tissue and capillaries with prominent endothelium. An initial diagnosis of well-differentiated liposarcoma was made. A 2.8-kg, encapsulated, yellowish gray mediastinal tumor was surgically removed. Mature adipose tissue intermingled with abundant thymic tissue containing numerous Hassall's corpuscles were seen histologically. Immunohistochemical markers for thymic epithelium, lymphoid tissue and adipocytes were all positive. Thymolipoma was the final diagnosis. The anemia subsided with resection of the tumor, and the patient was disease free 2.5 years after surgery.
  
  
  CONCLUSIONS
  To the best of our knowledge, this is the second report of a thymolipoma studied with FNAB. The criteria for the differential diagnosis between thymolipomas and other lipomatous tumours should be kept in mind.
authors.affiliation: Servicio de Patología, Hospital General de México, Dr. Balmis No. 148, Col. Doctores, Del. Cuauhtémoc, C.P. 06726, México, D.F. Mexico. monicaromero@att.net.mx
authors.forename: Mónica Belinda
authors.initials: MB
authors.lastname: Romero-Guadarrama
authors.forename: Marco A
authors.initials: MA
authors.lastname: Durán-Padilla
authors.forename: Humberto
authors.initials: H
authors.lastname: Cruz-Ortíz
authors.forename: Lisset
authors.initials: L
authors.lastname: Castro-Gómez
authors.forename: Dolores
authors.initials: D
authors.lastname: López-Vancell
authors.forename: Virginia
authors.initials: V
authors.lastname: Novelo-Retana
authors.forename: Ana Cecilia
authors.initials: AC
authors.lastname: Santiago-Prieto
authors.forename: Erika
authors.initials: E
authors.lastname: Fierro-Chávez
authors.forename: Héctor A
authors.initials: HA
authors.lastname: Rodríguez-Martínez
mesh_terms: D000328:Adult; D018951:Antigens, CD20 / Q000032:analysis; D044963:Biopsy, Fine-Needle; D002272:Carcinoembryonic Antigen / Q000032:analysis; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D016130:Immunophenotyping; D007633:Keratins / Q000032:analysis; D017493:Leukocyte Common Antigens / Q000032:analysis; D008067:Lipoma / Q000473:pathology*; D008080:Liposarcoma / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D008479:Mediastinal Neoplasms / Q000473:pathology*; D010503:Periodic Acid-Schiff Reaction; D013902:Radiography, Thoracic; D009418:S100 Proteins / Q000032:analysis; D013934:Thymectomy; D013953:Thymus Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D014057:Tomography, X-Ray Computed; D014746:Vimentin / Q000032:analysis
chemical_list: D018951:Antigens, CD20; D002272:Carcinoembryonic Antigen; D009418:S100 Proteins; D014746:Vimentin; D007633:Keratins; D017493:Leukocyte Common Antigens