Intracranial plasma cell granuloma: a report of four cases.

Inflammatory pseudotumors (IPT) are rare lesions composed of inflammatory cells admixed with collagen tissue. Although IPT are ubiquitous, intracranial locations are rare. In this study, four intracranial IPT of the plasma-cell-granuloma (PCG) type are reported. Four patients presented with lesions located, respectively, in the right cavernous sinus, the left cavernous sinus with extension to the tentorium cerebelli, the vermis cerebelli, and the pituitary stalk. All patients were operated on, but complete resection could not be achieved in cases 1 and 2. Follow-up was favorable in all cases, although case 1 still complained of headaches 2 years after operation. All cases were studied on histologic and immunohistochemical bases, and ultrastructural analysis was performed on two cases. In cases 1, 2, and 4, IPT were made up of plasma cells admixed with lymphocytes and rare histiocytes in a fibrous tissue-the density of which varied from case to case. In case 3, the mass was composed of plasma cells associated with numerous foamy histiocytes and polymorphonuclear cells. No light chain restriction could be demonstrated when immunohistochemistry was performed, and ultrastructural study did not disclose features reminiscent of meningioma or histiocytosis X. Intracranial IPT should not be confused with other diseases such as meningioma, lymphoproliferative disorders, or histiocytosis X. Although intracranial locations are much rarer than pulmonary ones, histology is identical in both sites and shows different patterns in its evolution. This is in agreement with the inflammatory origin of this lesion.