title: Morphological spectrum of peripheral nerve sheath tumors: An insight into World Health Organization 2013 classification.
abstract: BACKGROUND
  Peripheral nerve sheath tumors (PNSTs) are neuroectodermal in origin. Now these tumors are classified under World Health Organization (WHO) classification of tumors of soft tissue and bone 2013.
  
  
  OBJECTIVE
  To study the morphological spectrum of PNST and to study the secondary degenerative changes associated with it.
  
  
  METHODS
  This study was conducted from January 2010 to June 2015. The gross details of tumor and patient's demographic profiles were reviewed. The hematoxylin and eosin stained slides were reassessed and the lesions were categorized and classified as per the WHO 2013 classification. The tumors were also assessed for secondary degenerative changes.
  
  
  RESULTS
  Our study comprised 143 cases of PNST. Age of the patients ranged from 5 to 75 years. 21-30 years is the most common age of occurrence with head and neck being the most common site. The PNSTs observed in the present study were neurofibroma (NF) (61.5%), schwannoma (36%), malignant PNST (2%), and granular cell tumor (0.5%). Nearly 10% of NF fulfilled the criteria for neurofibromatosis 1 (NF1). Rare tumors such as plexiform schwannoma and granular cell tumor were also observed. Malignant tumors were larger in dimension than benign. Myxoid, cystic, and hyaline changes were commonly associated with benign tumors while necrosis, hemorrhage, and mitotic activity were seen with malignant tumors.
  
  
  CONCLUSIONS
  This series highlights the pathological variants of PNST along with their morphological changes and NF1 association. It is essential to be familiar with all these variants of PNST for accurate diagnosis as they have varied biological behavior.
authors.affiliation: Department of Pathology, Employees' State Insurance Corporation Medical College and PGIMSR, Bengaluru, Karnataka, India.
authors.forename: Panduranga
authors.initials: P
authors.lastname: Chikkannaiah
authors.affiliation: Department of Pathology, Employees' State Insurance Corporation Medical College and PGIMSR, Bengaluru, Karnataka, India.
authors.forename: Mythri M
authors.initials: MM
authors.lastname: Boovalli
authors.affiliation: Department of Pathology, Employees' State Insurance Corporation Medical College and PGIMSR, Bengaluru, Karnataka, India.
authors.forename: Velusamy
authors.initials: V
authors.lastname: Nathiyal
authors.affiliation: Department of Pathology, Employees' State Insurance Corporation Medical College and PGIMSR, Bengaluru, Karnataka, India.
authors.forename: Srinivasamurthy
authors.initials: S
authors.lastname: Venkataramappa
keywords: Granular cell tumor; malignant peripheral nerve sheath tumor; neurofibroma; neurofibromatosis; peripheral nerve; schwannoma