INFLAMMATORY PSEUDOTUMORS OF LYMPH-NODE ORIGIN SHOW MACROPHAGE-DERIVED SPINDLE CELLS AND LYMPHOCYTE-DERIVED CYTOKINE TRANSCRIPTS WITHOUT EVIDENCE OF T-CELL RECEPTOR GENE REARRANGEMENTS - IMPLICATIONS FOR PATHOGENESIS AND CLASSIFICATION AS AN IDIOPATHIC RETROPERITONEAL FIBROSIS-LIKE SCLEROSING IMMUNE-REACTION

Sclerosing pseudotumorous immune reactions of the retroperitoneum have been shown to consist of HLA-DR-positive spindle-shaped fibroblasts a nd macrophages that resemble fibroblasts, and in some instances they c ontain clonal populations of T lymphocytes not found in granulation ti ssue, keloids, nodular fasciitis, or fibromatoses. in patients who are iatrogenically immunosuppressed, circulating monocytes may be induced in vitro to transform into spindle-shaped macrophages, and secrete co llagen after stimulation by conditioning medium from activated T lymph ocytes. The authors investigated a series of five inflammatory pseudot umors (IPT) of lymph node origin for identification of spindle-shaped macrophages, T-cell receptor gene rearrangements, and lymphocyte-deriv ed cytokine mRNA production. All cases of IPT demonstrated spindle-sha ped macrophages resembling fibroblasts or myofibroblasts characterized by vimentin, CD45 (LCA), CD68 (KP1) or HAM-56, and HLA-DR(LN3) immuno reactivity and demonstrated production of procollagen-alpha 1 (I) mRNA by in situ hybridization. Clonal T-cell receptor chain gene rearrange ments were undetectable by polymerase chain reaction. Strong specific lymphocyte-derived interleukin-1 beta and interleukin-6 mRNA cytokine transcripts were identified. Although all patients with IPT were manag ed with steroids and nonsteroidal anti-inflammatory medication, some h ad treatment-refractory disease, Because all-trans retinoic acid has b een demonstrated to inhibit the in vitro transformation of monocytes i nto collagen-producing spindle-shaped macrophages (''neofibroblasts'') , it may be of benefit for patients with IPT.