Inflammatory pseudotumor of the spleen. A clinicopathologic and immunophenotypic study of eight cases.

We report the clinical, pathologic, and immunophenotypic findings of inflammatory pseudotumors of the spleen in eight patients. The primary importance of recognizing these uncommonly found lesions is to distinguish them from malignant lymphoma, which splenic inflammatory pseudotumors may mimic clinically and radiologically. Grossly, the splenic inflammatory pseudotumors in this study ranged from 0.5 to 11.5 cm. One case was multinodular, and seven lesions were solitary. In general, the size of the lesion correlated with the presence of symptoms. The smaller lesions were usually incidental findings, discovered as part of the workup of idiopathic thrombocytopenic purpura (three cases), during staging for Hodgkin's disease (one case), or at autopsy (one case). Microscopically, the lesions were composed of a variable mixture of inflammatory cells admixed within a spindle cell proliferation. Small, cytologically normal lymphocytes and plasma cells were constant features, in a variable mixture, with neutrophilic and eosinophilic leukocytes present in some cases. Coagulative necrosis was located centrally in six lesions; neutrophilic leukocytes were correlated with the presence of necrosis. The presence of necrosis did not correlate with the presence of symptoms. Immunohistochemical studies revealed that the small lymphocytes present were predominantly T cells. Histiocytes and polytypic plasma cells were also numerous, whereas B cells were infrequent. Inflammatory pseudotumors of the spleen are benign lesions. The clinical follow-up for the seven patients in this study who underwent splenectomy showed no evidence of recurrence or subsequent development of a hematopoietic neoplasm, with a median follow-up of 18 months (range, 3 to 135 months).