Contributed by Sufia Husain, MBBS, MD, FRCPath, Hisham MS Alkhalidi MBBS, FRCPC, Emad Raddaoui MD, FCAP, FASC
Dept of Pathology King Khalid Univ. Hospital, Riyadh, Saudi Arabia
A 38 year-old female, known case of diabetes insipidus presented with a progressively deteriorating left sided weakness, headache and bilateral papilledema. Her lipid profile was normal. Magnetic resonance imaging revealed a large right-sided frontoparietal mass (8.5x5.8x4.7 cm) with smooth displacement of adjacent brain parenchyma and mild midline shift (Figures 1 and 2). A smaller (1.4x1.2x0.6 cm) yet similar lesion was identified on the right side of the falx cerebri. Radiologic diagnosis of meningioma was made. The patient underwent right frontoparietal craniotomy. A small amount of tissue was sent to pathology for intraoperative diagnosis followed by total resection of the large frontoparietal lesion. The lesion in the falx cerebri was not resected in view of its small size and location. No adjuvant therapy was administered.
Fresh tissue fragment from the frontoparietal lesion was received in the laboratory for intraoperative diagnosis. Cytology and histology slides were prepared and stained with hematoxylin and eosin stains. Both cytology and histology revealed a multinucleated giant cell-rich lesion in a background of chronic inflammatory cells, mainly macrophages (Figure 3). There was no nuclear pleomorphism, mitotic activity or necrosis. The resected specimen consisted of a creamy-white, well circumscribed mass (9.0x7.0x5.0 cm) firmly adherent to the dura mater with a 2cm wide circumferential margin of uninvolved dura mater (Figure 4). Cut section was homogenous creamy-white. Representative sections were submitted for paraffin processing. A small amount of tissue was also submitted for electron microscopic study. On histology, the mass was comprised of diffuse sheets of large foamy cells, numerous multinucleated giant cells with classical Touton features (wreath-like arrangement of nuclei), interspersed lymphocytes and few plasma cells (Figure 5). Eosinophils and mitotic figures were rare. There was no necrosis. There was no appreciable nuclear pleomorphism or evidence of proliferation of meningothelial cells. On immunohistochemistry these foamy cells exhibited diffuse and strong positivity with CD68 (Figure 6) and vimentin. Some foam cells were positive with S-100. Stains like GFAP, EMA, SMA, ALK-1, CK and CD1a were negative. Ziehl-Neelsen stain for acid fast bacilli was negative. The adherent dura mater apart from being fibrotic appeared unremarkable. Electron microscopic studies showed that the foamy cells had numerous pseudopodia, lipid droplets and lysosomes confirming their histiocytic nature. Birbeck granules and tubular organelles of Langerhans cell histiocytosis were absent (Figure 7).