Primary lymphoma of bone presenting as monoarthritis

We report an unusual case of primary non-Hodgkin's lymphoma or reticulum cell sarcoma of bone presenting as monoarthritis in a middle-aged woman without previous rheumatic disease. She underwent rheumatologic evaluation of plasma and synovial fluid, synovial cytology, arthroscopy, synovial and bone biopsies. Our evaluation may be the most thorough rheumatologic one yet reported.