Meningioma

Lipoblastic, lipomatous or lipidized meningioma is an unusual extra-axial benign tumor. It shows benign clinical features and has a good prognosis after surgical excision. We present a 54-year-old woman with intracranial lipidized meningioma in the right temporal fossa, discuss the importance of the differential diagnosis among similar tumors and discuss the term 'Lipidized meningioma' in the light of the literature. [Neural Res 2003; 25: 764-766]

Keywords:: Lipidized; lipoblastic; meningioma

INTRODUCTION

The microscopic appearance of meningioma is highly variable, and different histological subtypes have been described1. Kasantikul2 attributed the diversity of meningioma to the pluripotential nature of the mesencymal cells arising from the neural crest. Lipidized meningioma is an unusual entity and this tumor was first described by Bailey and Bucy in 1931(3). Lipidized meningioma is characterized either by an admixture of mature adipocytes and meningioma or the production of triglycerides by neoplastic meningothelial cells assuming lipoblast-like appearance4. The mechanism underlying fat accumulation in meningioma is unclear. Lipidization is accepted as a metaplastic change because of the capacity of meningothelial cells to differentiate along various mesenchymal cell lines. These tumors can be classified in the metaplastic meningioma category. Both the 1993 and 2000 World Health Organization Classification of Tumors of the Nervous System have included lipid-laden meningiomas within the metaplastic meningioma group, together with meningothelial tumors containing bone, cartilage and myxoid tissue3. We report a lipidized meningioma as an unusual case.

CASE REPORT

A 54-year-old woman suffering from headache and central visual impairment over two years was admitted to our neurosurgery department. Neurological examination was normal. Magnetic resonance imaging (MRI) showed an apparent extra-axial right temporal mass and T^sub 1^ weighted images showed a double component neoplasm consisting of a large hypointense and a small homogeneously hyperintense component. After contrast medium the neoplasm was homogeneously hyperintense (Figure 1). A right temporal craniotomy was performed and a well-circumscribed grayish-pink extraaxial mass in the base of the right temporal fossa was totally removed.

Macroscopically, the tumor was 1.8 x 1x 0.5 cm in size and had a smooth surface. On cut section, it had yellow-brown color. Microscopically, the tumor was composed of adipocyte-like cells and conventional meningothelial cells. The majority of lipidized meningothelial cells resembled the mature adipocytes (Figure 2). The proportion of fatty cells was between 70%-80%. Mitoses and necrosis were absent. There was prominent focal vascularity. Microcystic component was seen in a few areas. Immunohistochemically, tumor cells were positive for epithelial membrane antigen (EMA), vimentin and negative for glial fibrilary acidic protein (GFAP) and S-100 protein (Figure 3). Thus, morphological and immunohistochemical findings were corresponded with a lipidized meningioma. The patient was discharged on the fourth post-operative day, and has encountered no recurrence in the follow-up period.

DISCUSSION

Intracranial meningioma is a common neoplasm and accounts for 15% of all primary intracranial neoplasm1,2. The histopathologic classification of meningiomas in widest use today was proposed by Courville and later modified by Russel and Rubinstein5. Meningiomas are divided into four major categories: fibroblastic, transitional, syncytial and angioblastic. The spectrum of differentiation is thought to reflect the pluripotency of the arachnoidal cap cells from which meningiomas originate5. Occasionally, this pluripotential cells may undergo transformation into another cell type of mesencymal origin and, thus some unusual histological subtypes, lipomatous, osseous, xanthomatous, myxomatous, microcystic, are revealed1,3,6.

Actually, fat accumulation most often occurs in meningothelial and transitional meningiomas3, whereas the term 'lipidized' meningioma has been used to designate meningothelial neoplasm containing cells that, to varying degrees, resemble adipocytes or lipoblast. The proportion of lipid component in tumors is variable and changes between 10%-90%. Although the majority of tumors featured adipocyte-like cells, only infrequently numerous lipidized cells lead us to suggest a diagnosis of lipoma. Less often the cells contained one or several small lipid droplets, with the appearance being that of lipoblast in such tumors that mimick signetring cell carcinoma3. In this respect, differential diagnosis is important among lipidized meningiomas and tumors such as liposarcoma, intracranial metastatic signet-ring carcinoma or chordoma6. While the later tumors have poor prognosis, lipidized meningiomas have good prognosis. If lipidization is marked, distinction between lipidized meningioma and lipoma may be difficult. Immunostaining for EMA and negative staining for collagen IV generally resolve the problem3. The clinical features and prognosis of lipidized menin giomas do not differ from those of usual benign meningiomas1. Local recurrence is very rare3. In our case, almost the entire tumor was composed of adipocyte-like cells. The whorls of conventional meningothelial cells were seen within lipoma-like tissue.

Immunohistochemically, cells of lipidized meningioma are reactive for EMA, vimentin and S-100 protein and negative for GFAP1,3,4,6. Roncaroli et al.3 reported that both conventional and lipid-laden meningothelial cells showed membrane immunreactivity for EMA and weak, only focal reactivity for S-100 protein. Lattes et al.6 reported three lipoblastic meningiomas and found EMA reactivity in the meningothelial component, not in adipocyte or lipoblast- like cells. In our case, we found adipocyte-like cells to be immunreactive for EMA and vimentin but no expression of S-100 protein and GFAP was found. Ultrastructually, lipid-laden neoplastic cells shared same features of meningothelial cells such as cytoplasmic intermediate filaments, interdigitating cell processes, and well formed desmosomes3. According to the reported immunohistochemical and ultrastructural features of lipidized meningiothelial cells, neoplastic cells have neither lipocytes nor lipoblastic features. Roncaroli et al.3 suggested that the accumulation of lipid in meningothelial cells reflects a metabolic abnormality of the neoplastic cells rather than a true metaplasia. Because of this, the term 'lipidized meningioma' may be a more appropriate name than lipoblastic or lipomatous meningioma for the full spectrum of lipid-containing meningothelial tumors.

CONCLUSION

In this report, we presented a rare lipidized meningioma with immunohistochemical features. Its recognition is important for prognostic purpose in view of the excellent clinical outcome after excision.

REFERENCES

1 Mariniello G, Spaziante R, Del Basso De Caro ML, de Divitiis E. An unusual case of lipoblastic meningioma of the falx cerebri. Clin Neurol Neurosurg 2000; 102: 180-185

2 Kasantikul V, Brown WJ. Lipomatous meningioma associated with cerebral vascular malformation. J Surg Oncol 1984; 26: 35-39

3 Roncaroli F, Scheithauer BW, Laeng RH, Cenacchi G, Abell-Aleff P, Moschopulos M. Lipomatous meningioma: A clinicopathologic study of 18 cases with special reference to the issue of metaplasia. Am J Surg Pathol 2001; 25: 769-775

4 Vajtai I, Elek P, Varga Z, Dibuz M, Kapin M, Zs Toth E. Lipomatous meningioma: Report of two cases and review of the literature. Orv Hetil 2000; 141:1079-1083

5 Liebig T, Hoffmann T, Hosten N, Sander B, van Landeghem F, Stoltenburg-Didinger G, Lanksch WR. Lipomatous secretory meningioma: Case report and review of the literature. Neuroradiology 1998; 40: 656-658

6 Lattes R, Bigotti G. Lipoblastic meningioma: 'Vacuolated meningioma'. Hum Pathol 1991; 22: 164-171

F. Bolat*, F. Kayaselcuk*, M.V. Aydin[dagger], B. Erdogan[dagger], S. Ulusan[double dagger] and S. Zorludemir[sec]

* Department of Pathology, [dagger] Department of Neumsurgery, [double dagger] Department of Radiology Baskent University Faculty of Medicine, Adana Teaching and Medical Research Center, Adana [sec] Department of Pathology, Cukurova University Faculty of Medicine, Adana, Turkey

Correspondence and reprint requests to: Dr Filiz Bolat, Baskent Universitesi, Patoloji A.D., Adana Hastanesi, Yuregir 01250, Adana, Turkey, [drfilizbolat@yahoo.com] Accepted for publication March 2003.

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