Inflammatory pseudotumor of the spleen. Morphological, radiological, immunophenotypic, and ultrastructural features.

A case of inflammatory pseudotumor of the spleen is described. Its rapid enlargement, demonstrable by ultrasound studies and computed tomographic scan, its gross appearance, and some of its histologic features suggested malignant lymphoma. However, a characteristic circumferential zonal pattern and polytypic immunophenotype helped to establish the correct diagnosis. In retrospect, the zonal pattern was also identified radiologically.