title: A large mediastinal benign myoepithelioma effacing the entire hemithorax: case report with literature review.
abstract: BACKGROUND
  Myoepithelial neoplasms, although sometimes encountered in soft tissues are described very rarely in mediastinum and lung. We reported a rare case of such a tumor which was very large in size and not connected to respiratory tree.
  
  
  METHODS
  A 24 year old male presented with blunt chest pain and respiratory distress. A CT scan was performed which showed large heterogeneously enhancing soft tissue mass occupying the left hemithorax. It measures 18.5 X 15.8 X 7.6. Thoracotomy with excision of the tumor was done. Operative findings include multilobulated and nodular large glistening white tumor located in anterior mediastinum adherent to parietal pleura and effacing the pulmonary parenchyma. However tumor was not connected or seems to originate from trachea or lung. Microscopic sections show neoplastic lesion composed of nests, cords and trabeculae of small to medium sized cells with round nuclei and clear cytoplasm. Background showed myxoid appearance with areas of cartilaginous differentiation. Immunohistochemical expression of CKAE1/AE3, p63, ASMA, S100 and GFAP favored the diagnosis of benign myoepithelioma.
  
  
  CONCLUSIONS
  Myoepithelial tumors are rare soft tissue tumors thought to arise from stem cells capable of divergent differentiation and occur anywhere in the body. Histopathologic recognition of these tumors is essential as these tumors may behave in a benign fashion despite large sizes.
authors.affiliation: Department of Histopathology, Liaquat National Hospital and Medical College, Karachi, Pakistan. doc_atif2005@yahoo.com.|Intern, Liaquat National Hospital and Medical College, Karachi, Pakistan. doc_atif2005@yahoo.com.|Dhaka Medical College, Dhaka, Bangladesh. doc_atif2005@yahoo.com.
authors.forename: Atif Ali
authors.initials: AA
authors.lastname: Hashmi
authors.affiliation: Department of Histopathology, Liaquat National Hospital and Medical College, Karachi, Pakistan. amna.khurshid@lnh.edu.pk.|Intern, Liaquat National Hospital and Medical College, Karachi, Pakistan. amna.khurshid@lnh.edu.pk.|Dhaka Medical College, Dhaka, Bangladesh. amna.khurshid@lnh.edu.pk.
authors.forename: Amna
authors.initials: A
authors.lastname: Khurshid
authors.affiliation: Department of Histopathology, Liaquat National Hospital and Medical College, Karachi, Pakistan. Naveen.faridi@lnh.edu.pk.|Intern, Liaquat National Hospital and Medical College, Karachi, Pakistan. Naveen.faridi@lnh.edu.pk.|Dhaka Medical College, Dhaka, Bangladesh. Naveen.faridi@lnh.edu.pk.
authors.forename: Naveen
authors.initials: N
authors.lastname: Faridi
authors.affiliation: Department of Histopathology, Liaquat National Hospital and Medical College, Karachi, Pakistan. muzzamil10@hotmail.com.|Intern, Liaquat National Hospital and Medical College, Karachi, Pakistan. muzzamil10@hotmail.com.|Dhaka Medical College, Dhaka, Bangladesh. muzzamil10@hotmail.com.
authors.forename: Muhammad Muzzammil
authors.initials: MM
authors.lastname: Edhi
authors.affiliation: Department of Histopathology, Liaquat National Hospital and Medical College, Karachi, Pakistan. mehmoodkhan955@yahoo.com.|Intern, Liaquat National Hospital and Medical College, Karachi, Pakistan. mehmoodkhan955@yahoo.com.|Dhaka Medical College, Dhaka, Bangladesh. mehmoodkhan955@yahoo.com.
authors.forename: Mehmood
authors.initials: M
authors.lastname: Khan
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D001706:Biopsy; D002637:Chest Pain / Q000209:etiology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008479:Mediastinal Neoplasms / Q000737:chemistry / Q000150:complications / Q000473:pathology* / Q000601:surgery; D009208:Myoepithelioma / Q000737:chemistry / Q000150:complications / Q000473:pathology* / Q000601:surgery; D012120:Respiration Disorders / Q000209:etiology; D013908:Thoracotomy; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D047368:Tumor Burden; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor