We　investigate　the　behavior　of　heat　conduction　in　two-dimensional　(2D)　electron　gases　without　and　with　a　magnetic　field.　We　perform　simulations　with　the　multiparticle　collision　approach,　suitably　adapted　to　account　for　the　Lorenz　force　acting　on　the　particles.　For　zero　magnetic　field,　we　find　that　the　heat　conductivity　kappa　diverges　with　the　system　size　L　following　the　logarithmic　relation　kappa　＜^＞　ln　L　(as　predicted　for　2D　systems)　for　small　L　values;　however,　in　the　thermodynamic　limit　the　heat　conductivity　tends　to　follow　the　relation　kappa　＜^＞　L1/3,　as　predicted　for　one-dimensional　(1D)　fluids.　This　suggests　the　presence　of　a　dimensional-crossover　effect　in　heat　conduction　in　electronic　systems　that　adhere　to　standard　momentum　conservation.　Under　the　magnetic　field,　time-reversal　symmetry　is　broken　and　the　standard　momentum　conservation　in　the　system　is　no　longer　satisfied　but　the　pseudomomentum　of　the　system　is　still　conserved.　In　contrast　with　the　zero-field　case,　both　equilibrium　and　nonequilibrium　simulations　indicate　a　finite　heat　conductivity　independent　on　the　system　size　L　as　L　increases.　This　indicates　that　pseudomomentum　conservation　can　exhibit　normal　diffusive　heat　transport,　which　differs　from　the　abnormal　behavior　observed　in　low-dimensional　coupled　charged　harmonic　oscillators　with　pseudomomentum　conservation　in　a　magnetic　field.　These　findings　support　the　validity　of　the　hydrodynamic　theory　in　electron　gases　and　clarify　that　pseudomomentum　conservation　is　not　enough　to　ensure　the　anomalous　behavior　of　heat　conduction.