title: Olfactory neuroblastoma: A clinicopathological experience of a rare entity from Pakistan.
abstract: OBJECTIVE
  To present the clinicopathological experience of Olfactory Neuroblastoma (ONB) with emphasis on histopathological and immunohistochemical features.
  
  
  METHODS
  A descriptive cross-sectional study was done on 36 cases of ONB, selected by non-probability purposive sampling. Theses cases of ONB were retrieved and reviewed from surgical pathology database of Aga Khan University Hospital reported between January 1993 and March 2015.
  
  
  RESULTS
  Tumor size and age of presentation was wide in range without any distinct bimodal distribution. Nasal cavity was most common site along with involvement of paranasal sinuses. More than 50% cases had Kadish stage A. Microscopically, most cases were Grade-1 and majority showed partial or complete lobular architecture. Neurofibrillary matrix was observed in 2/3(rd) of cases. Among immunohistochemical markers, Neuron Specific Enolase was most frequently expressed. Unusual positive expression of Cytokeratin AE1/AE3 and Cytokeratin CAM5.2 was also seen focally in few cases.
  
  
  CONCLUSIONS
  The ONB has great variability of histological and clinical presentation, and immunohistochemical markers are useful to differentiate from more common small round blue cell tumours of nasal cavity.
authors.affiliation: Dr. Saroona Haroon, MBBS, FCPS (Histopathology). Consultant and Histopathology Dept. Chair, Department of Pathology and Laboratory Medicine, Prince Faisal Cancer Centre, King Fahad Specialist Hospital, Buraidah, Kingdom of Saudi Arabia.
authors.forename: Saroona
authors.initials: S
authors.lastname: Haroon
authors.affiliation: Dr. Muhammad Usman Tariq, MBBS, FCPS (Histopathology). Instructor, Section of Histopathology, Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Karachi, Pakistan.
authors.forename: Muhammad Usman
authors.initials: MU
authors.lastname: Tariq
authors.affiliation: Dr. Aisha Memon, MBBS, FCPS (Histopathology). Assistant Professor and Consultant, Section of Histopathology, Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Karachi, Pakistan.
authors.forename: Aisha
authors.initials: A
authors.lastname: Memon
authors.affiliation: Dr. Saira Fatima, MBBS, FCPS (Histopathology). Assistant Professor and Consultant, Section of Histopathology, Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Karachi, Pakistan.
authors.forename: Saira
authors.initials: S
authors.lastname: Fatima
authors.affiliation: Dr. Sheema Habibul Hasan, MBBS, FRCPath. Professor and Consultant, Section of Histopathology, Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Karachi, Pakistan.
authors.forename: Sheema Habibul
authors.initials: SH
authors.lastname: Hasan
keywords: Esthesioneuroblastoma; Immunohistochemistry; Olfactoryneuroblastoma; Sinonasal tract