Sorry to hear that. Well its better to consult your oncologist before going liposuction to know his lymphoma status whether its in regression and his general health condition and immunity is in good condition.If all conditions favours and he's in good state he can perform liposuction.Its important to see clinically if his arm skin tone is good enough so there will be no complication.
As time is concern, it can just be performed as a day-care surgery,but atleast 7-10 days followup is required,but yea it depends upon professional to professional.