I am new to this forum and have been researching lymphoma since that is the diagnosis my 6 yr old Lab has received. His also began with hind leg weakness and was misdiagnosed as lyme. He showed knuckling in the front leg and general cognitive impairment, ie. confusion, getting lost. The vet believes that the cancer has spead to his neurological system at this point. His lymph nodes are now enlarged, but I suspect that he had this disease for awhile. I hope it is not lymphoma.