CORRESPONDENCE: Reader Submitted Cases of the Month
Edited by Dr Ronald L. Hamilton
OCTOBER 2007 CASE 1: A 72‐YEAR‐OLD WOMAN WITH RIGHT FRONTAL EXTRA‐AXIAL MASS

CLINICAL DETAILS

A 72‐year‐old woman presented with 1‐year history of memory disturbance. Magnetic resonance imaging (MRI) showed a right frontal extra‐axial hyperdense mass of 4.6 × 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.

MICROSCOPIC EXAMINATION

Large pieces were submitted for examination. Histology showed a meningioma with multifocal accumulation of numerous large cells with abundant eosinophilic cytoplasm and displaced nuclei (Figure 1). In addition, some classical plasma cells, lymphocytes and mast cells were also detected (Figure 2). In the large eosinophilic cells, lamellar inclusions and needle‐shaped crystals were noted (Figure 3), particularly on semi‐thin section (Toluidine Blue) (Figure 4).

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Immunohistochemistry by EMA revealed positivity in the meningeal cells and there was also some staining in the plasma cells and the large cells (Figure 5). The crystal‐containing cells were strongly positive by CD68 (PGM1) (Figure 6). CD79a showed strong positivity in the plasma cells and a slightly fainter staining in the crystal‐storing large cells (Figure 7). The plasma cells and most crystal containing cells expressed both kappa (Figure 8) and lambda light chains (Figure 9) (although the staining was fainter in the latter), with a strong kappa predominance. The proliferation activity was only 3% by Ki67.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Electron microscopy from the paraffin‐embedded material showed that the nuclear features of the crystal‐storing cells and the plasma cells were very similar (Figure 10). The crystals had predominantly needle or rectangular shape, but occasional triangular inclusions were also seen (Figure 11)). Occasional plasma cells showed some osmiophilic inclusions, similar to those found in the large cells (Figure 12).

Figure 10.

Figure 11.

Figure 12.

DIAGNOSIS

Plasma cell predominant lymphoplasmacytic‐rich meningioma, grade I (WHO), with crystalline inclusions.

DISCUSSION

Although the large cells resembled rhabdoid cells, the tumor cells were cytologically different and lacked increased proliferative activity. Immunoreactivity for CD79a and light chains, together with the ultrastructural features, confirmed the plasma cell origin of those large cells. The inflammatory component of this lymphoplasmacytic‐rich meningioma consisted predominantly of plasma cells. Although plasma cell predominant lymphoplasmacytic‐rich meningioma is not uncommon 1, 7, to our knowledge, similar crystalline inclusions in plasma cells have not been reported previously in meningioma.

There is an inconsistency about the terminology of inclusion bearing plasma cells in the literature. There are a few published cases with plasma cell predominant inflammatory lesions in the stomach and the oesophagus, having been called Russell body gastritis or Mott cell gastritis 4, 5, 6, 11, 12. One of these cases showed plasma cells with crystalline inclusions similar to our case (5). However, Russell bodies were originally described as having round hyalin‐like inclusions by electron microscopy and these were not found in our case (8). Therefore, we felt that using terminology such as “Mott cell predominant meningioma” may not be entirely correct.

Crystalline plasma cell inclusions are not uncommon in lymphoplasmacytoid tumors and are thought to be more suggestive of a diagnosis of lymphoma over a reactive process 2, 3. In our case, the features of the inclusions were most like those described in crystal‐storing histiocytosis (CSH). CSH is an uncommon phenomenon (less than 100 cases reported so far) with presence of inclusion‐containing plasma cells and histiocytes, also involving the bone marrow 9, 10. It is almost always associated with expression of monoclonal immunoglobulins (multiple myeloma, monoclonal gammopathy of undetermined significance, lymphoplasmacytic lymphoma, extramedullary plasmacytoma), and only occasional cases of CSH have been reported without paraproteinemia (9). It is presumed to be an intralysosomal accumulation of secreted paraproteins or immunoglobulins, which aggregate in crystals. Immunoglobulins of kappa light chain type have been almost exclusively involved without a consistent association with a particular heavy chain (10). This suggests that CSH results from the storage of crystals produced by plasma cell tumors that either overproduce light chain or express a structurally aberrant molecule.

In our case, we noticed excess of kappa‐positive cells, but no obvious monoclonal plasma cell proliferation was seen. Although the large cells were positive with CD68, there was no indication of bone marrow involvement; therefore, usage of the term CSH was not justified. However, the mechanism of crystal formation might well be similar to CSH.

ABSTRACT

We present a case of plasma cell predominant lymphoplasmacyte‐rich meningioma with numerous crystalline inclusions. A 72‐year‐old woman presented with 1‐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.