CD20 (pan-B cell antigen) expression on bone marrow-derived T cells.

Antibodies directed against CD20 (L26, Leu 16, and B1) are frequently used to determine the presence of B lymphocytes. However, recent publications describe the unexpected presence of CD20-positive T cells in the peripheral blood of normal subjects and occasional T-cell neoplasms that express CD20. To determine the presence of CD20-positive T cells in bone marrow, flow cytometric analysis was performed on 34 aspirate specimens (14 normal, 5 acute lymphoblastic lymphoma [ALL], 5 acute myelogenous leukemia [AML], 4 HIV positive, 2 myelodysplastic/myeloproliferative, 2 chronic myelogenous leukemia [CML], 1 chronic lymphocytic lymphoma [CLL], 1 multiple myeloma). A small population of cells coexpressing CD3 (Leu 4) and CD20dim (Leu 16) was identified in 94% of the specimens, representing 0% to 11% (mean 1.77%) of marrow mononuclear cells and 0% to 22.2% (mean 6.54%) of marrow lymphoid cells. There was no correlation between the percentage of CD20-positive T cells and the CD4:CD8 ratio, patient age, gender, or diagnosis. CD20dim positive cells included immature B cells and CD20-positive T cells. Although evaluation of CD20 expression is useful in delineating B-cell processes, caution should be exercised in interpreting its expression on bone marrow T-lymphoid cells. CD20 expression on T cells may be seen in either normal, reactive, or neoplastic processes.

Epstein-Barr virus and lymphoproliferation in methotrexate-treated rheumatoid arthritis.

Generalized lymphadenopathy developed in a 60-year-old female receiving methotrexate and prednisone for treatment of rheumatoid arthritis. Histologic examination of an enlarged right axillary lymph node revealed effacement of normal architecture by a polymorphic population of lymphocytes. The recognition that the patient was medically immunosuppressed and the similarity of lymph node histology to that of a polymorphic post-transplantation lymphoid proliferation led to suspicion that the adenopathy might represent an immunosuppression-related lymphoid proliferation. This possibility was supported by regression of the adenopathy on discontinuation of methotrexate, despite continued corticosteroid therapy, which is an outcome reminiscent of the remissions observed with reduction of immunosuppressive therapy in post-transplantation lymphoproliferative disorders. Subsequent ancillary laboratory studies of lymph node tissue included genetic probe analysis, which revealed a monoclonal population of B-lymphocytes containing clonal Epstein-Barr virus DNA. In situ hybridization studies performed on lymph node tissue revealed expression of Epstein-Barr virus-encoded RNA 1 transcripts, and immunohistochemical studies revealed expression of Epstein-Barr virus latent membrane protein 1. These ancillary studies confirmed the similarity to post-transplantation lymphoproliferative disorder. Although immunosuppression-related lymphoproliferative disorders share features with malignant lymphoma, the possibility of resolution in situations in which immunosuppression can be reversed provides a distinction from true malignancy and is of profound importance in therapeutic decision making.

Transitional cell carcinoma arising within a paratubal cyst: report of a case.

We report the clinical and morphologic features of a transitional cell carcinoma (TCC) that arose within a paratubal cyst of the right broad ligament. This case represents only the second report of a TCC arising in the broad ligament and the first with documented origin within a paratubal cyst. A possible explanation for this tumor's histogenesis as it relates to the more common transitional cell neoplasms of the ovary is presented.