title: Mast cells and matrix metalloproteinase 9 expression in actinic cheilitis and lip squamous cell carcinoma.
abstract: OBJECTIVE
  The aim of this study was to evaluate mast cell (MC) density and migration and their association with matrix metalloproteinase (MMP) 9 expression in squamous cell carcinoma (SCC) and actinic cheilitis (AC).
  
  
  METHODS
  Tryptase, c-Kit, and MMP-9 expression was evaluated in 20 cases of SCC, 20 cases of AC, and 7 cases of normal lip (control samples) by immunohistochemistry techniques.
  
  
  RESULTS
  Tryptase(+) and c-Kit(+) MC densities were significantly higher in SCCs than in ACs and control samples (P < .001). However, no significant difference was found when comparing tryptase(+) and c-Kit(+) MC densities between ACs and control samples (P values .185 and .516, respectively). MMP-9 was strongly expressed in SCCs and moderately expressed in ACs and control samples. A highly significant association was found between tryptase(+) MC density and the expression of MMP-9 (P < .001).
  
  
  CONCLUSIONS
  The increase in MC density associated with the strong expression of MMP-9 may favor SCC progression.
authors: Oral Pathology Graduate Program, Department of Dentistry, Federal University of Rio Grande do Norte, Natal, Brazil.
authors: Valéria
authors: V
authors: Souza Freitas
authors: Pedro Paulo
authors: PP
authors: de Andrade Santos
authors: Roseana
authors: R
authors: de Almeida Freitas
authors: Leão
authors: L
authors: Pereira Pinto
authors: Lélia Batista
authors: LB
authors: de Souza