Atypical lymphoplasmacytic and immunoblastic proliferation from rheumatoid arthritis: a case report.

A case of atypical lymphoplasmacytic and immunoblastic proliferation (ALPIBP) in the lymph nodes associated with well-documented rheumatoid arthritis (RA) is presented. A 68-year-old Japanese female with a 6-year history of RA presented with right neck lymphadenopathy of 3 months duration. A biopsy specimen showed paracortical hyperplasia and numerous lymphoid follicles. On high-power field, the paracortical area was diffusely infiltrated by a polymorphous population consisting of numerous mature plasma cells, plasmacytoid cells, immunoblasts, including Hodgkin-like cells, small- to medium-sized lymphocytes, and histiocytes. Immunohistochemical study demonstrated that immunoblasts usually were CD20+, and a portion of them was CD30+. The histomorphological findings of the present case are similar to those of methotrexate (MTX)-induced atypical lymphoproliferative disorders (LPDs) in some aspects. However, Epstein-Barr virus-encoded small RNA-positive cells were not identified by in situ hybridization. The polytypic nature of B lymphocytes also was demonstrated by immunohistochemistry and polymerase chain reaction. Moreover, there was no history of MTX therapy in the present case, indicating that MTX-induced, LPD-like ALPIB may occur even in the RA patients not treated with MTX therapy.