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We report the case of a Kaposi-like variant of splenic angiosarcoma in a 28-year-old woman. The tumor featured a Kaposi sarcoma-like spindle cell proliferation with slit formation and markedly dilated spongelike vascular channels filled with erythrocytes. Thirteen months following the initial splenectomy, metastatic lesions were found in the patient's liver and bone marrow. The proliferating cells were positive for factor VIII-associated antigen and CD34. The human herpesvirus 8 genome, which is regarded as a diagnostic feature of Kaposi sarcoma, was not detected by polymerase chain reaction analysis. Although the histologic findings were similar, this Kaposi-like variant of splenic angiosarcoma must be considered distinct from Kaposi sarcoma.

Context: Inflammatory pseudotumor is an uncommon and enigmatic lesion. The spindle cells found in this tumor have features of myofibroblasts. Because of the indefinite relationship of these lesions with inflammatory fibrosarcoma and their indefinite biologic behavior, inflammatory pseudotumor is currently classified as inflammatory myofibroblastic tumor (IMT). To date, only case reports or small series have been published on these tumors, which are primary in the spleen., Design: In this study, we describe the clinical, morphologic, and immunophenotypic findings of 12 cases of splenic IMT and examine their relationship to Epstein-Barr virus (EBV)., Results: The patients included 8 women and 3 men, ranging from 19 to 77 years of age (mean, 53 years; median, 60 years). Demographic data were unavailable for 1 patient. Patients generally presented with abdominal pain (n = 5) and fever (n = 4). Associated lesions included renal cell carcinoma (n = 2), colonic adenocarcinoma (n = 1), and cholecystitis (n = 1). All tumors were composed of a bland spindle cell proliferation in association with a variable mixed inflammatory component. There were 2 growth patterns, namely, a cellular spindle cell pattern and a hypocellular fibrous pattern. An immunohistochemical panel confirmed the myofibroblastic nature of the spindle cells. The spindle cells of 2 cases were immunoreactive for EBV latent membrane protein 1, whereas 6 of 10 cases were positive for EBV-encoded RNA using in situ hybridization. Follow-up was available for 8 patients; 6 were alive with no evidence of recurrence and 2 were dead of other causes., Conclusion: Splenic IMTs are uncommon lesions that can be distinguished from other conditions using a combination of clinical, histologic, and immunophenotypic findings. Epstein-Barr virus may play a role in the pathogenesis of splenic IMT, and there may be an association of splenic IMT with concomitant disease or malignancy. Most splenic IMTs have an excellent long-term prognosis.