for my $key (keys %mappings) {
    for (keys %{$mappings{$key}}) {
        next if $mappings{$key}{$_} < 2;
        print "$key - $mappings{$key}{$_} -> $_\n" ;
    }
}

##</code><code>##

lung cancer - 2 -> some cancer
cancer - 4 -> foot cancer