title: Glial fibrillary acidic protein and CD57 immunolocalization in cell block preparations is a useful adjunct in the diagnosis of pleomorphic adenoma.
abstract: BACKGROUND
  The cytologic distinction between pleomorphic adenoma (PA) and adenoid cystic carcinoma (ACC) can be diagnostically challenging in aspirate smears. Hence a cytologic diagnosis of "atypical cytology" with a differential diagnosis including PA and ACC is occasionally rendered in a subset of salivary gland fine-needle aspirations.
  
  
  OBJECTIVE
  To evaluate the role of glial fibrillary acidic protein (GFAP) and CD57 expression in cell block material obtained during fine-needle aspiration procedure in differentiating PA from ACC.
  
  
  METHODS
  We performed GFAP and CD57 immunostains on formalin-fixed, paraffin-embedded cell block sections of 26 salivary gland fine-needle aspiration cases with the following cytologic diagnoses: (1) PA (10 cases); (2) atypical cytology, cannot exclude ACC (8 cases); and (3) ACC (8 cases).
  
  
  RESULTS
  All 10 (100%) cases with cytologic diagnoses of PA were positive for GFAP, and 8 (80%) of 10 cases were positive for CD57; tissue follow-up confirmed the diagnosis of PA in all cases. All 8 (100%) cases with cytologic diagnosis of ACC were negative for both GFAP and CD57; tissue follow-up confirmed the diagnoses of ACC in all cases. Of the 8 cases with diagnoses of atypical cytology, 4 (50%) were negative and 4 (50%) were positive for both GFAP and CD57. Subsequent tissue follow-up in these cases revealed 4 cases of ACC (all negative for GFAP and CD57) and 4 cases of PA (all positive for GFAP and CD57).
  
  
  CONCLUSIONS
  Our results show that positive staining for GFAP and CD57 serves as a useful adjunct for the diagnosis of PA and helps to reduce the uncertainty in challenging cases.
authors.affiliation: Department of Pathology, SUNY-Upstate Medical University, Syracuse, NY, USA.
authors.forename: Sejal S
authors.initials: SS
authors.lastname: Shah
authors.forename: Vishal S
authors.initials: VS
authors.lastname: Chandan
authors.forename: David C
authors.initials: DC
authors.lastname: Wilbur
authors.forename: Kamal K
authors.initials: KK
authors.lastname: Khurana
mesh_terms: D008949:Adenoma, Pleomorphic / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D044963:Biopsy, Fine-Needle; D018959:CD57 Antigens / Q000235:genetics / Q000378:metabolism*; D003528:Carcinoma, Adenoid Cystic / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology; D003937:Diagnosis, Differential; D015972:Gene Expression Regulation, Neoplastic; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016612:Paraffin Embedding; D012468:Salivary Gland Neoplasms / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D012469:Salivary Glands / Q000378:metabolism / Q000473:pathology