Contributed by Istvan Bodi, MD, Tibor Hortobágyi, MD and Stefan Buk
Department of Clinical Neuropathology, King's College Hospital, London, UK
We present a case of plasma cell predominant lymphoplasmacyte-rich meningioma with numerous crystalline inclusions. A 72-year old woman presented with one-year history of memory disturbance and an MRI revealing a right frontal extra-axial mass. Histology showed a benign meningioma with multifocal accumulation of numerous large cells with abundant eosinophilic cytoplasm, filled with lamellar inclusions and bipyramidal crystals. In addition, some classic plasma cells, mastocytes and lymphocytes were also detected. The crystal containing cells were positive by CD79a and PGM1 and expressed polyclonal light chains, with kappa predominance. Electron microscopy showed crystals with needle or rectangular shape in plasma cells. Plasma cell inclusions have been reported occasionally in reactive inflammatory lesions but more frequently in plasma cell tumors and lymphoplasmacytic lymphoma, maybe associated with crystal-storing histiocytosis. Although plasma cell predominant lymphoplasmacyte-rich meningioma is not uncommon, to our knowledge, similar crystalline inclusions in plasma cells have not been reported previously in meningioma.
A 72-year old woman presented with one-year history of memory disturbance. MRI showed a right frontal extra-axial hyperdense mass of 4.6 x 5.4 cm with surrounding parenchymal edema and associated midline shift. The patient underwent craniotomy and resection of the tumor. She had an uneventful post-operative period. There was no history of hematological disease. She was symptom-free on follow-up after 6 months.
Large pieces were submitted for examination. Histology showed a meningioma with multifocal accumulation of numerous large cells with abundant eosinophilic cytoplasm and displaced nuclei (Fig. 1A and 1B). In addition, some classical plasma cells, lymphocytes and mastocytes were also detected (Fig. 2A and 2B). In the large eosinophilic cells lamellar inclusions and needle-shaped crystals were noted (Fig. 3), particularly on semithin section (Toluidine Blue) (Fig. 4).
Immunohistochemistry by EMA revealed positivity in the meningeal tumor cells and there was also some staining in the plasma cells and the large cells (Fig. 5). The crystal containing cells were strongly positive by CD68 (PGM1) (Fig. 6). CD79a showed strong positivity in the plasma cells and a slightly fainter staining in the crystal-storing large cells (Fig. 7). The plasma cells and most crystal containing cells expressed both kappa (Fig. 8) and lambda light chains (Fig. 9) (although the staining was fainter in the latter), with a strong kappa predominance. The proliferation activity was only 3% by Ki67.
Electron microscopy from the paraffin embedded material showed that the nuclear features of the crystal-storing cells and the plasma cells were very similar (Fig. 10). The crystals had predominantly needle or rectangular shape, but occasional triangular inclusions were also seen (Fig. 11). Occasional plasma cells showed some osmiophilic inclusions, similar to those found in the large cells (Fig. 12)