title: Myoepithelioma of the parotid gland initially diagnosed by fine needle aspiration cytology and immunocytochemistry: a case report.
abstract: BACKGROUND
  Myoepithelioma is a rare, benign tumor of the salivary gland, most commonly affecting the parotid gland. Although the cytologic features of myoepithelioma are documented in a few case reports, it has rarely been diagnosed preoperatively by fine needle aspiration (FNA) cytology.
  
  
  METHODS
  A 33-year-old man presented with a left parotid swelling 2.5 cm in diameter and of about 5 years' duration. FNA smears showed bundles of spindle-shaped cells as well as plasmacytoid and stellate cells in sheets and dissociated forms. A few cells had nuclear grooves, and occasional cells showed intranuclear cytoplasmic inclusions. In May-Grünwald-Giemsa-stained smears, most of the cells had reddish cytoplasm. Red to purple, myxoid matrix was present as a scanty fibrillar substance and as globules surrounded by tumor cells vaguely reminiscent of adenoid cystic carcinoma. A cytodiagnosis of myoepithelioma was given and corroborated by immunocytochemical staining, which revealed a positive reaction for vimentin, smooth muscle actin and S-100 protein. Epithelial membrane antigen yielded a negative reaction except for a few plasmacytoid cells with weakly positive staining. Histopathology of the resected tumor and immunohistochemical staining confirmed the cytodiagnosis of myoepithelioma.
  
  
  CONCLUSIONS
  FNA cytologic features together with immunocytochemical studies on smears can offer a preoperative diagnosis of myoepithelioma.
authors.affiliation: Department of Pathology, Faculty of Medicine, Kuwait University, Safat, Kuwait. dilip76@hotmail.com
authors.forename: Dilip K
authors.initials: DK
authors.lastname: Das
authors.forename: Bahiyah E
authors.initials: BE
authors.lastname: Haji
authors.forename: Mahmoud S
authors.initials: MS
authors.lastname: Ahmed
authors.forename: Mohamad N Riyad
authors.initials: MN
authors.lastname: Hossain
mesh_terms: D000328:Adult; D044963:Biopsy, Fine-Needle; D003581:Cytodiagnosis; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D009208:Myoepithelioma / Q000175:diagnosis* / Q000473:pathology*; D010307:Parotid Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D009418:S100 Proteins / Q000737:chemistry; D013194:Staining and Labeling
chemical_list: D009418:S100 Proteins