Several independent cosmological tests have shown evidences that the energy density of the Universe is dominated by a dark energy component , which cause the present accelerated expansion . The large scale structure formation can be used to probe dark energy models , and the mass function of dark matter haloes is one of the best statistical tools to perform this study . We present here a statistical analysis of mass functions of galaxies under a homogeneous dark energy model , proposed in the work of Percival ( 2005 ) , using an observational flux-limited X-ray cluster survey , and CMB data from WMAP . We compare , in our analysis , the standard Press-Schechter ( PS ) approach ( where a Gaussian distribution is used to describe the primordial density fluctuation field of the mass function ) , and the PL ( Power Law ) mass function ( where we apply a nonextensive q-statistical distribution to the primordial density field ) . We conclude that the PS mass function can not explain at the same time the X-ray and the CMB data ( even at 99 % confidence level ) , and the PS best fit dark energy equation of state parameter is \omega = -0.58 , which is distant from the cosmological constant case . The PL mass function provides better fits to the HIFLUGCS X-ray galaxy data and the CMB data ; we also note that the \omega parameter is very sensible to modifications in the PL free parameter , q , suggesting that the PL mass function could be a powerful tool to constrain dark energy models .