Hello. Welcome to HCM.
Having a positive family history and yourself suffering from RA (or any other autoimmune disorder) definitely increases the risk of lymphoma. But it does not mean that you definitely have lymphoma. Your scheduled tests are absolutely correct and will definitely help in forming an ap41propriate diagnostic. If required a repeat biopsy
and FNAC can also be done. You also have chance of having tuberculosis
are very common in both) So its best to wait for results and let clinician act accordingly.
Bast of Luck.