Isolated plasma cell granuloma of the meninges

Abstract

A 77-year-old female with hypertension, presented with right partial motoric seizures. Neurological examination showed right hemiparesis. Brain MRI revealed extensive post-contrast interhemispheral dural, pachymeningeal and leptomeningeal enhancement of the left cerebral hemisphere (Fig. 1), which were initially interpreted as meningeal carcinomatosis. However, CSF analysis performed on two occasions, with normal cell count, glucose and protein levels, did not show malignant cells. Chest and abdominal CT scan and mammography were normal. Brain and meningeal biopsies were performed and histological findings (Fig. 2) were consistent with plasma cell granuloma. Following this bone marrow biopsy, skeletal X-rays survey, peripheral blood cell count, renal function, calcium and protein electrophoresis were normal. The patient was treated with corticosteroids without any neurological sequel and significant improvement of MRI findings. This case emphasizes how the diagnosis of leptomeningeal carcinomatosis remains challenging, as neither CSF cytology nor MRI is adequately sensitive for the diagnosis. Plasma cell granulomas are uncommon, benign inflammatory masses of unknown etiology [1]. They are histologically characterized by polyclonal plasma cells, large histiocytes with lymphophagocytosis and fibrosis [1]. There are only few reports of isolated CNS plasma cell granuloma in the literature [1]. Based on similar histological features, plasma cell granulomas, Rosai–Dorfman disease, and idiopathic hypertrophic pachymeningitis are now believed to form a spectrum of inflammatory or reactive conditions with, probably, the same unknown etiology [2, 3]. Rosai–Dorfman disease, or sinus histiocytosis, with massive lymphadenopathy, is a benign idiopathic histiocytic proliferative disease with pathognomonic histological and immunohistochemical characteristics. Extranodal involvement occurs in 43 % of cases [4], and by December 2008 111 cases of Rosai–Dorfman disease involving the central nervous system had been reported in the literature [5]. The main histopathological differentiation between plasma cell granuloma and Rosai–Dorfman disease is a careful appraisal of the morphological features together with the absence of emperipolesis in the S100-positive D. Kolenc S. Dotlic Department of Pathology, University Hospital Center Zagreb, Zagreb, Croatia