Dear Lynsey
I haven't treated anyone with lymphoma. Presumably you mean you're going to treat the person, not their lymphoma? Sorry to split hairs but the title's a bit misleading . I would just say, get as much information as you can about them including what treatment they have had or are having. If they are being treated by an oncologist, you can get them to inform their consultant that they want to have reflexology (or write to that person yourself). Many hospital cancer centres have complementary therapies so the chances are the oncologist will give their approval gladly. Reflexology can be a very welcome treatment for someone with cancer, in terms of helping with side effects of treatment and supporting emotional and spiritual well-being. When you have cancer people may act oddly around you and distance themselves as their own way of coping, and your client may be in need of a warm human touch and a sympathetic person. If the person is having chemo, treating them before a session may help them to relax and be less nervous about it. If they don't have a Hickman line but have the drugs injected into their hand, some hand reflexology or simply hand massage may help prepare their veins for the canulla (spelling? it's the needle they put in your vein) being inserted. I hope this person benefits from their treatments with you, and that you find it a good experience too.
If you want to read up on cancer in general, there are some excellent resources on Cancer Bacup, Breast Cancer Care, Macmillan and probably other websites.
Good luck!