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Plasmacytoid T-zone cell proliferation in a patient with chronic myelomonocytic leukemia. Histologic and
1Department of Pathology, Massachusetts General Hospital, Boston 02114.
Insights
Plasmacytoid T-zone cells in lymph nodes are distinct from myeloid leukemia cells. Immunophenotyping suggests a monocytic lineage, but they are not direct precursors or part of the neoplastic clone in myelomonocytic leukemia.
Area of Science:
- Hematology
- Immunology
- Oncology
Background:
- Plasmacytoid T-zone cells are distinctive cells found in reactive lymph nodes.
- Tumorous proliferations of these cells have been linked to myelomonocytic leukemias.
- The precise nature and relationship of these cells to myeloid leukemia remain unclear.
Observation:
- A case report of a 64-year-old woman with chronic myelomonocytic leukemia presenting with lymphadenopathy due to plasmacytoid T-zone cell accumulation.
- The spleen also showed aggregates of these cells alongside extramedullary hematopoiesis.
- Lymphadenopathy resolved with treatment, and the patient died 7 years later from blast transformation of her leukemia.
Findings:
- Plasmacytoid T-zone cell aggregates were morphologically and immunophenotypically distinct from leukemic myeloid infiltrates.
- Immunohistochemistry showed positivity for CD68 and CD43, but not myeloid lineage markers.
- No evidence of differentiation into myeloid or monocytic cells was observed.
Implications:
- The findings suggest plasmacytoid T-zone cells may originate from the monocytic lineage.
- These cells are likely not direct precursors of mature myeloid or granulocytic cells.
- The study indicates plasmacytoid T-zone cells may not be part of the neoplastic clone in myelomonocytic leukemia.
Abstract:
The term "plasmacytoid T-zone cells" has been used to describe distinctive cells that occur in clusters in the paracortex of some reactive lymph nodes. Recently, tumorous proliferations of these cells have been described in several patients with myelomonocytic leukemias. Neither the nature of these cells nor their relationship to myeloid leukemia has been conclusively established. We report the case of a 64-year-old woman with chronic myelomonocytic leukemia who developed lymphadenopathy that proved to be due to tumorous accumulation of plasmacytoid T-zone cells in the interfollicular regions of the lymph nodes. She underwent splenectomy because of symptomatic splenomegaly; the resected spleen also contained aggregates of plasmacytoid T-zone cells, in addition to extramedullary hematopoiesis. On treatment with busulphan and prednisone, the lymphadenopathy resolved and did not recur. The patient died 7 years later with blast transformation of her myelomonocytic leukemia and no recurrence of lymphadenopathy. The aggregates of plasmacytoid T-zone cells were architecturally and cytologically distinct from the leukemic infiltrates of myeloid cells in the spleen, and there was no evidence of differentiation of these cells into myeloid or monocytic cells. A panel of monoclonal antibodies on paraffin sections revealed no lineage-specific T- or B-cell markers (UCHL1-, L26-), and the plasmacytoid cells were positive for CD68 (KP1) and L60 (CD43), as well as faintly positive for 4KB5 (CD45RA) and MB1 (CD45R). They did not stain with antibodies to myeloid lineage antigens CD15, lysozyme, or myeloperoxidase. The combination of clinical, morphologic, and immunologic features of plasmacytoid T-zone cells in this case suggests that these cells may be of monocytic lineage but are not direct precursors of mature monocytic or granulocytic cells, and may not be part of the neoplastic clone in patients with myelomonocytic leukemia.