Lipomatous meningioma: a clinicopathologic study of 18 cases with special reference to the issue of metaplasia

Histopathology of Meningiomas

Meningiomas are considered to arise from meningothelial cells, whose cytomorphology they recapitulate. In this chapter, we review the characteristic histological features of meningioma, including classic architectural and cytological features. There exists a broad spectrum of morphological variants of meningioma. The 2021 WHO Classification recognizes nine benign (grade 1), three intermediate-grade (grade 2), and three malignant (grade 3) variants. We review the characteristic histological features of these meningioma variants, describe immunohistochemical stains, which may assist with establishing a diagnosis, and discuss differential diagnostic considerations that may prove challenging for a diagnosis of meningioma.

Visual Aura Secondary to Supratentorial Lipomatous Meningioma: A Rare Case Report

Background/Aim: Lipomatous meningioma is a rare type of meningioma that is formed as the result of an accumulation of lipids inside the cell due to metabolic activity dysregulation. It differs from other types of meningiomas in its radiological and immunohistochemical characteristics. We report a rare case of a patient treated in our department for this particular type of meningioma who developed a type of migraine with the aura component as the first clinical symptom. Case Report: A 55-year-old woman presented with a migraine and reported having phosphenes in recent years. Head Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) scans were performed; these showed an extensive hypodense and hypointense formation located in the left parieto-occipital region. This formation was implanted in the tentorium region, with a prevailingly adipose-type signal intensity. The patient underwent an occipital craniotomy with the total removal of the lesion. The histological examination indicated a lipomatous metaplastic meningioma. Conclusion: We reported the first case of a lipomatous meningioma presenting with a migraine with a visual aura. Seizures and headaches can be included as possible symptoms. According to the current literature, lipomatous meningiomas affect women more commonly than men. The patient of our reported case presented visual disturbances in the form of a visual aura, which occurred 10 years before finding the meningioma, and surgery dramatically improved the symptoms and quality of life.

A rare case of xanthomatous meningioma

Xanthomatous meningioma is an extremely rare subtype of metaplastic meningiomas with few cases reported in the literature. Histopathologically, it is composed of oval-shaped cells that have central nuclei and cytoplasm with lipid-filled vacuoles, resembling macrophages. Here, the authors present a case of xanthomatous meningioma and discuss the hypotheses related to its origin and the differential diagnosis. A 40-year-old woman presented with an increased headache complaint over the past month. A computed tomography scan revealed a heterogeneous mass on the right parietal lobe, following which a right craniotomy was done. Microscopic examination showed neoplastic meningothelial cells with whorl formation and areas of xanthomatous changes. Both meningothelial and xanthomatous cells were positive with vimentin, progesterone, and epithelial membrane antigen. CD68 and lysozyme were expressed only in the xanthomatous component, and there was no expression with periodic acid-Schiff (PAS) stain and PAS–diastase. As the diagnostic criteria of atypical meningioma were not observed, a diagnosis of xanthomatous meningioma, WHO grade I, was made. Owing to the characteristic xanthomatous changes, its differential diagnosis includes grade II clear cell meningioma, Rosai–Dorfman disease, and hemangioblastoma. To avoid misidentifying these cells as macrophages, a high degree of awareness of this unique subtype of meningioma is required.

Intraosseous metaplastic meningioma: A case report

Metaplastic meningioma is a rare World Health Organization Grade I meningioma subtype, accounting for 0.2%-1.6% of all meningiomas. Primary extradural meningiomas represent less than 2% of all meningiomas, with intraosseous meningioma as a subtype of primary extradural meningiomas. Herein, we report the case of a 65-year-old male presenting with headache. His computed tomography scans showed an osteolytic left parietal bone mass, and magnetic resonance imaging revealed hyperintense dots in the mass on T1-weighted images. The mass was then resected and diagnosed on histopathological examination as an intraosseous metaplastic meningioma.

A Rare Variant of Meningioma: Case Report and Review of Literature

Meningioma is a morphologically heterogeneous tumour arising from meningothelial cells that has been classified by the World Health Organization into 15 different histological types and graded into three types groups (Grade I, II, and III) based on the biological behavior. Metaplastic meningioma is a rare subtype of meningioma characterized by focal or widespread mesenchymal differentiation in the form of bone, cartilage, fat, or xanthomatous tissue elements. Xanthomatous meningioma is a subclass of metaplastic meningioma which is exceedingly rare. Only a few cases have been reported in the literature. Here, we report the case of a 44-year-old man, who presented with left sided weakness and was diagnosed as a case of xanthomatous meningioma.

Pathology of meningiomas

Meningiomas are a diverse group of neoplasms that exhibit a wide range of morphologies and clinical behavior. They are generally accepted to originate from arachnoid cap cells within the leptomeninges. Classic histologic features include whorl formations, psammoma bodies, nuclear holes, and nuclear pseudoinclusions. Meningiomas are classified as benign, atypical, or anaplastic (grades I, II, or III) based on histologic features including mitotic activity, brain invasion, and presence of other minor criteria. There are numerous histologic variants of meningiomas, and some are associated with worse clinical outcomes and therefore are assigned a higher grade. The majority of meningiomas show diffuse positivity for vimentin and epithelial membrane antigen, supporting the dual mesenchymal and epithelial nature of meningothelial cells. The presence of an elevated proliferation index (as measured by Ki-67 immunohistochemical stain) and loss of progesterone receptor expression are associated with the higher grade. Pathologic features including histologic variants, grading criteria, and ancillary tests such as special and immunohistochemical stains are discussed.

Lipomatous meningioma: A rare subtype of benign metaplastic meningiomas

Lipomatous meningiomas are extremely rare subtypes of benign meningiomas and are classified as metaplastic meningioma in the World Health Organization classification. We present a 77-year-old man presented with the history of a gradually intensifying headache for the last 3 months. A right frontoparietal mass was detected on his cranial magnetic resonance imaging. The patient was operated on via a right frontoparietal craniotomy, and histopathological diagnosis was lipomatous meningioma. Distinctive characteristics of lipomatous meningiomas were discussed with special emphasis to importance of immunohistochemical examinations, particularly for its differentiation from the tumors showing similar histology though having more aggressive character.

Co-Existence of Atypical Meningioma, Intratumoral Lipometaplasia and Extensive Hyperostosis of Calvarium: A Rare Entity

Background

Lipomatous meningiomas are a rare variety of meningioma, in which fat storage occurs in adipocytes and lipoblasts are found within the tumor. World Health Organization grade II atypical meningiomas with lipometaplasia and extensive hyperostosis of calvarium is a rare type with a good prognosis after complete removal.

Case Description

Here we report a case of intracranial atypical meningioma with lipometaplasia and disproportionately large hyperostosis of overlying calvarium in a 40-year-old man. His computed tomography and magnetic resonance imaging scans showed right frontotemporoparietal homogenous bony swelling with an underlying diffusely enhancing extra-axial, dural-based lesion with areas of hyperintensity on T1 and isointensity on T2 with perilesional edema. Microscopically, it revealed a meningeal neoplasm with hypercellularity, small cell changes, sheathing pattern, and extensive lipomatous metaplasia.

Conclusions

World Health Organization grade II atypical meningiomas with lipometaplasia and extensive hyperostosis of calvarium is a rare type with a good prognosis after complete removal. Clinical features in patients are similar to those of conventional meningioma; however, radiologic features depend on the amount of fat present in the tumor. To the best of our knowledge, there are no case reports in the current literature regarding this. Every new case will widen our horizon. Meningothelial cells exhibit lipomatous changes as a result of metabolic abnormalities.

Two Different Meningioma Variants in the Same Tumor: A Rare Histopathological Finding

We report a case of meningioma with both secretory and lipomatous features in an advanced middle aged female patient with a 3-month history of headaches and convulsions. Radiological findings are revised and compared to other reported cases in the literature.

Xanthomatous meningioma: A metaplastic or degenerative phenomenon?

Xanthomatous changes can be observed in various conditions including primary xanthomatosis that is linked to an underlying hypercholesterolemia and more commonly associated with secondary xanthomatous degenerative processes in neoplasm and chronic inflammation. Meningioma with extensive xanthomatous change is exceedingly rare. The presence of cholesterol clefts within this peculiar meningioma subtype has not been described. Herein, we report an unusual case of xanthomatous meningioma in an 83-year-old normolipidemic woman, who presented to us with worsening lower limb weakness and global aphasia. There was increasing evidence to suggest that the presence of xanthomatous changes in long-standing meningioma is merely a sequela of cellular degeneration rather than true metaplastic change as previously hypothesized. Hence, the diagnosis of "xanthomatous meningioma" in the metaplastic category should be revisited and considered as a distinct histological subtype. The possible histogenesis of such intriguing phenomenon is discussed with a review of the literature.

Pilocytic Astrocytoma with Adipocytic Differentiation: A Rare Histological Variation

Lipidization of the low-grade astrocytic tumor is a very rare phenomenon. We report a case of pilocytic astrocytoma with adipocytic differentiation involving the left cerebellar hemisphere and pontis in an 11-year-old boy. Till date, very few such cases have been reported in children. A young boy presented with a clinical picture suggestive of cerebellar dysfunction since 7 months. Imaging revealed a mass lesion involving the left cerebellar hemisphere measuring 4.5×4.1cm. Subtotal excision of the tumor was carried out. Microscopic features were typical of pilocytic astrocytoma but with extensive lipidization of tumor cells. Immunohistochemically, the tumor cells were immunoreactive to glial fibrillary acidic protein, S-100, and immunonegative to p53 and isocitrate dehydrogenase 1. Ki-67 labeling index was 1%. The patient had an uneventful postoperative period and is doing well on follow-up. An extensive review of prior work was carried out to elucidate the clinicopathologic significance of this entity, if any, with special reference to the pediatric age group.

Uncommon Cranial Meningioma: Key Imaging Features on Conventional and Advanced Imaging

Given the high incidence of intracranial meningiomas encountered in clinical practice, it is not uncommon to find rare subtypes of meningioma, with unusual imaging findings. These commonly represent a diagnostic challenge. In this article, we review the imaging appearance of typical meningioma on conventional and advanced imaging as well as the key imaging features of multiple uncommon subtypes: cystic, microcystic, lipomatous, chordoid, angiomatous, intraosseous, extracranial, atypical/malignant, and tumor-to-tumor metastasis (also known as collision tumors). Some of these uncommon subtypes, however, demonstrate imaging features that may allow for a more specific diagnosis, or features, which can influence patient's management.

Lipomatous meningioma: Case report and review of the literature

Lipomatous meningiomas are a very rare form of brain meningiomas consisting of fat accumulation within the tumor. Magnetic resonance imaging (MRI) or computerized tomographic (CT) imaging can be utilized to visualize the fat accumulations, but histopathologic staining is necessary in order to make a definitive diagnosis. The key histopathologic feature is the identification of adipocyte-like cells within the tumor, but other markers have also been identified. In this case report and review of the literature, we discuss how to recognize the symptoms associated with lipomatous meningiomas and the definitive treatment approach for these rare tumors.

Lipomatous Change in Uveal Melanoma: Histopathological, Immunohistochemical and Cytogenetic Analysis

PURPOSE

The aim of this study was to describe a case of lipomatous change in uveal melanoma.

PROCEDURES

The patient presented with a 2-year history of blurry vision. A full examination of the right eye revealed a dome-shaped pigmented subretinal mass in the choroid with a thickness of 9 mm and a diameter of 15 mm. The eye was enucleated and prepared for histopathologic, genetic and molecular investigation.

RESULTS

Histopathology revealed a small circumscribed area consisting of mature adipocytic appearing cells with abundant clear cytoplasm and small peripheral flattened nuclei within a spindle-cell melanoma of the uvea. The cytoplasm of the adipocytic cells stained negative for periodic acid-Schiff and Alcian blue and positive for Melan-A, HMB-45 and tyrosinase, confirming melanocytic lineage. Fluorescence in situ hybridization analysis confirmed trisomy of chromosome 6p22 and disomy of chromosome 3p13 in the nuclei of both the tumor spindle type B cells and in the nuclei of lipomatous tumor cells.

CONCLUSIONS

Lipomatous change can be added to the many histopathologic faces of uveal melanoma. To our knowledge, this is the first report of lipomatous change in uveal melanoma performed with cytogenetic investigations.

Revisiting Lipomatous Meningioma: A Case Report and Review of an Unusual Entity

Lipomatous meningioma is a very rare subtype of metaplastic meningioma. It is defined by the presence of adipocytic-like cells, which are thought to result from lipid accumulation in meningothelial cells or true metaplastic change. We report a case of a lipomatous meningioma arising in a female patient complaining of recent seizures. Imaging studies revealed a 4-cm dural-based mass, with severe perilesional edema. Histologically, the tumor was composed of meningothelial whorls intermixed with adipocytic-like cells. No atypical criteria or brain invasion were found. The 2 components have differences in progesterone receptor expression and Ki-67 labeling, which may suggest that adipocytic-like cells may represent some quiescent form of meningothelial neoplastic cells, characterized by metabolic abnormalities, leading to lipid accumulation and very low proliferative activity. Lipomatous meningioma should also be kept in mind when considering the differential diagnosis of dural lesions with vasogenic edema in the absence of brain invasion.

Intraosseous lipomatous meningioma

A 49-year-old man with intermittent headaches and right sided parietal lump was found to have an intraosseous right parietal lesion on computed tomography (CT) and magnetic resonance imaging (MRI). A stereotactic craniectomy and excision of the lesion were performed with histopathology confirming features consistent with primary lipomatous meningioma with intraosseous extension. Lipomatous meningiomas are very uncommon subtype of meningiomas, with ongoing discussions as to their true pathogenesis. To our knowledge this case represents the first reported case of a lipomatous meningioma with predominant intraosseous extension.

Lipidized or lipomatous meningioma, which is more appropriate? A case report

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.

Clinicopathological analysis of metaplastic meningioma: report of 15 cases in Huashan Hospital

OBJECTIVE

Metaplastic meningioma is a rare subtype of benign meningiomas, classified as WHO grade I with well prognosis. Here we presented our experiences on 15 cases of metaplastic meningioma, to investigate the clinicopathological features, therapies and prognosis of these cases.

METHODS

15 patients underwent surgical treatment for intracranial metaplastic meningioma between 2001 and 2010 at Neurosurgery Department of Huashan Hospital, Shanghai, China. The clinical data, radiological manifestation, treatment strategy, pathological findings and prognosis of all patients were analyzed retrospectively.

RESULTS

Among the 15 cases (10 males and 5 females), the age ranged from 22 to 74 years old (the mean age was 50.67-year old). The clinical manifestations include headache, dizziness, seizure attack, vision decrease, and weakness of bilateral lower limbs. All the patients received surgical treatment, combined with radiotherapy in some cases. In the follow-up period, recurrence occurred in 2 cases, of which 1 patient died of other system complications.

CONCLUSIONS

Metaplastic meningiomas are characterized by focal or widespread mesenchymal differentiation with formation of bone, cartilage, fat, and xanthomatous tissue elements. Surgical removal is the optimal therapy, and the overall prognosis is well. But recurrence may occur in some cases, thus radiotherapy is necessary for such kind of patients.

Lipidized glioblastoma: pathological and molecular characteristics

We report a rare case of a 33-year-old man with a lipidized glioblastoma multiforme (GBM) in the right posterior frontal region. Histologically the tumor had all the typical features of a GBM but with the rare observation of lipidized differentiation. There were multiple mitoses, extensive vascular proliferation, focal necrosis and the tumor cells had abundant xanthomatous cytoplasm and marked nuclear pleomorphism. The tumor showed immunoreactivity with GFAP. The O(6) - methylguanine methyltransferase (MGMT) promoter was methylated and there were no isocitrate dehydrogenase (IDH)1 and IDH2 mutations. To the best of our knowledge, this is the first time MGMT promoter status and IDH mutation assessment have been reported in a case of lipidized GBM.

Myxoid meningioma: a rare metaplastic meningioma variant in a patient presenting with intratumoral hemorrhage

Myxoid (metaplastic) meningioma is a rare WHO Grade I meningioma subtype arising from the leptomeninges. It has unique Alcian blue stromal staining and distinctive cellular interdigitations, junctional complexes, and nucleolar pseudoinclusions on ultrastructural pathology that help to distinguish it from other meningioma variants. The authors describe the case of a rare left middle fossa, extraaxial myxoid meningioma in a 50-year-old woman to emphasize the important histological characteristics and observations essential for making a precise diagnosis. To their knowledge this is the seventh reported case of a myxoid meningioma in the literature and the sixth case in an adult; however, it is the first reported instance of myxoid meningioma in a patient presenting with intratumoral hemorrhage.

Intracerebral metaplastic meningioma with prominent ossification and extensive calcification

We present a patient (male 26 years) with a short history of recurrent seizures induced by a largely intracerebrally located frontal lobe meningioma. The tumor displayed a heretofore unpublished combination of extensive metaplastic bone formation and prominent non-psammomatous calcifications with focal chicken-wire pattern.

Unclassified glioneuronal tumor with advanced lipidization

Lipidization is observed only occasionally in primary neuroectodermal tumors of the central nervous system. It may reflect lipomatous transformation of tumor cells into xanthomatous and/or adipocyte-like cells. We report a unique case of mixed glioneuronal tumor with marked lipomatous changes in a young patient with intractable epilepsy. MRI revealed a well-circumscribed lesion in the right temporal lobe. Histopathological findings showed the pleomorphic tumor with numerous cells containing large lipid droplets, resembling mature adipocytes, that were arranged in clusters or scattered within the neoplastic tissue. The tumor was composed of both glial and neuronal elements. Some tumor cells displayed features intermediate between glial and neuronal cells. The reticulin fibers were limited to blood vessels. Mitotic figures, vascular proliferation, and necrosis were absent, and MIB-1 labeling index was less than 1%. Diffuse immunoreactivity for GFAP and S100-protein was observed. In some heavily lipidized cells, the lipid droplets were surrounded by a cytoplasmic rim of GFAP immunoreactivity. Numerous cells exhibited immunostaining for NSE and synaptophysin. This is the first documented case of glioneuronal tumor with extensive lipomatous transformation, which might be considered as a heavily lipidized unclassified pleomorphic glioneuronal tumor or a variant of lipoganglioglioma with marked pleomorphism and severe lipidization.

Glycogen-rich pleomorphic xanthoastrocytoma with clear-cell features: confirmatory report of a rare variant with implications for differential diagnosis

Central nervous system space-occupying lesions with clear-cell features encompass a nosologically heterogeneous array, ranging from reactive histiocytic proliferations to neuroepithelial or meningothelial neoplasms of various grades and to metastases. In the face of such differential diagnostic breadth, recognizing cytoplasmic lucency as part of the morphological spectrum of some low grade gliomas will directly have an impact on patient care. We describe a prevailing clear-cell change in an epileptogenic left temporal pleomorphic xanthoastrocytoma surgically resected from a 36-year-old man. Mostly subarachnoid and focally calcified, the tumor was composed of fascicles of moderately atypical spindle cells with optically lucent cytoplasm that tended to intermingle with a desmoplastic mesh of reticulin fibers. Immunohistochemically, coexpression of S100 protein, vimentin, GFAP, and CD34 was noted. Conversely, neither punctate staining for EMA nor positivity for CD68 was seen. Mitotic activity was absent, and the MIB1 labeling index was 2-3% on average. Diastase-sensitive PAS-positive granula indicated clear-cell change to proceed from glycogen storage. Electron microscopy showed tumor cell cytoplasm to be largely obliterated by non-lysosomal-bound pools of glycogen, while hardly any fat vacuole was encountered. Neither ependymal-derived organelles nor annular lamellae suggesting oligodendroglial differentiation were detected. The latter differential diagnosis was further invalidated by lack of codeletion of chromosomal regions 1p36 and 19q13 on molecular genetic testing. By significantly interfering with pattern recognition as an implicit approach in histopathology, clear-cell change in pleomorphic xanthoastrocytoma is likely to suspend its status as a "classic", and to prompt more deductive differential diagnostic strategies to exclude look-alikes, especially clear-cell ependymoma and oligodendroglioma.

Lipoglioblastoma: a lipidized glioma radiologically and histologically mimicking adipose tissue

BACKGROUND

We report the case of a man with glioblastoma containing a component radiologically and histologically mimicking adipose tissue.

CASE DESCRIPTION

A 48-year-old man recently complaining of headaches and difficulty with speech presented with a cystic peripherally enhancing left temporoparietal mass with focal intrinsically (precontrast) bright nodules in fluid attenuated inversion recovery and T1-weighted images similar to adipose tissue. Histologically, the enhancing component was classic glioblastoma, whereas the bright nodules comprised tumor cells that in aggregate closely resembled adipose tissue.

CONCLUSIONS

The case illustrates the extent to which lipidized central nervous system tumors of glial origin, or components thereof, can radiologically and histologically resemble adipose tissue. However, immunohistochemical staining and electron microscopy can eliminate diagnostic confusion.

Lipoastrocytoma: Case report and review of the literature

Lipoastrocytoma is an extremely rare tumor, with only six cases described. We report the case of an astrocytoma involving the upper part of the cerebellar-pontine angle and the right portion of the clivus starting from the brainstem with a diffuse lipomatous component in a 39 year-old man. The patient was admitted with headache of 1 year's duration and diplopia over the previous 3 months. MRI revealed a ponto-cerebellar lesion that showed irregular enhancement after contrast administration. Subtotal excision of the tumor was accomplished. Adjuvant chemotherapy and radiation therapy were not administered. Histologically the tumor showed the classical histology of low-grade astrocytoma and a portion of the lesion was composed of lipid-laden cells. Immunohistochemistry for glial fibrillary acid and S-100 proteins clearly demonstrated the glial nature of these cells. Ki-67/Mib-1 labeling index was low (2%). The patient remains in good neurological conditions after 10 months. Our case has a benign postoperative behavior, also after subtotal excision, with restrictions due to the short follow-up. It is important to record each new case of this rare tumor to produce a better characterization of this lesion.

Lipomatous meningioma with concomitant acute subdural hematoma--case report--

A 55-year-old man presented with a rare lipomatous meningioma associated with acute subdural hematoma manifesting as sudden onset of severe headache, but no neurological deficit. No evidence of trauma or underlying predisposition to hemorrhage was seen. Fluid-attenuated inversion-recovery magnetic resonance imaging showed a thin hyperintense area in the right temporal convexity, and an extra-axial mass appearing as mixed hypointensity and hyperintensity. Two weeks later, right temporal craniotomy was performed and the tumor was totally resected with the attached dura. The hematoma was localized at the inferior margin of the mass and connected directly with the tumor. Histological examination of the resected specimen revealed typical meningothelial meningioma admixed with mature adipose tissue. Longstanding intratumoral congestion probably caused hyaline deposition in the tissue, leading to vessel rupture.

A case of metaplastic meningioma with extensive xanthomatous change

We report a case of metaplastic meningioma with extensive xanthomatous change occurring in a 61-year-old woman. Magnetic resonance imaging demonstrated a well-demarcated, dura-based mass measuring 7 cm in maximal diameter in the right occipital to parietal area. Under a clinical diagnosis of meningioma, right parietal craniotomy was performed. Histologically, the tumor showed extensive xanthomatous change together with the common features of meningothelial meningioma. Tumor cells showed diffuse xanthomatous change in various quantities, and xanthomatous tumor cells frequently showed a gradual transition to the non-xanthomatous counterpart. The xanthomatous tumor cells showed immunopositivity for epithelial membrane antigen (EMA), vimentin, fatty acid synthase and several histiocytic markers (CD68, Ki-M1p, MAC387, lysozyme, alpha 1-antitrypsin and alpha 1-antichymotrypsin). In addition, there was patchy infiltration of foamy macrophages. Since these histiocytes did not show immunopositivity for EMA, these cells were distinguished from the xanthomatous tumor cells. These two types of xanthomatous changes comprised approximately two-thirds of the whole tumor tissue. Any atypical features such as necrosis, frequent mitotic figures or brain parenchymal invasion were not observed. We diagnosed this case as xanthomatous meningioma, WHO grade I.

Lipomatous meningioma

We present a case of intracranial lipomatous meningioma in the parietal convexity in a 64-year-old woman. The mass showed low density on computed tomography, was hyper-intense on T1-weighted magnetic resonance images, and had decreased intensity upon imaging with fat-suppressed sequences. Gross total removal of the tumor was performed. Histopathologically, the tumor was a meningioma with mixed transitional and lipomatous patterns. Immunohistochemically, the meningothelial foci were positive for epithelial membrane antigen (EMA) and vimentin, and negative for S-100 protein. The lipomatous foci were positive for EMA, vimentin, and S-100 protein. The Ki-67 index values of the meningothelial and lipomatous foci were 1.0% and 1.8%, respectively. We review previous reports of lipomatous meningioma and discuss its clinical presentations and pathology.

Lipomatous meningioma: report of 2 cases and review of the literature

BACKGROUND

Lipomatous meningioma is a rare but, most of the time, benign tumor. Its pathogenesis is still debated: it is usually considered to be part of the metaplastic meningioma, but several authors recently suggested that fat accumulation inside the tumor was related to metabolic disorders of the meningothelial cells.

CASES DESCRIPTION

We report 2 cases of lipomatous meningioma. Both patients were women older than 60 years. One patient suffered from headache and seizures, the other one presented with behavioral disturbance. Radiological features depended on the amount of fat accumulation within the tumor. Surgical treatment allowed complete resection in both cases without any complications. Both meningiomas were of transitional-type and were apparently composed of 2 populations of cells: meningothelial cells and lipid-laden cells resembling mature adipocytes. Immunohistochemical study showed that lipid-laden cells expressed EMA, CD99, and progesteron receptor, favoring a meningothelial differentiation rather than an adipocytic lineage.

CONCLUSION

Our study strongly suggests that lipomatous meningioma results from an accumulation of lipid inside meningothelial cells rather than a true metaplasia.

Méningiome lipomateux

Lipomatous meningiomas are rarely encountered and are included in the World Health Organization's (WHO) group of metaplastic meningiomas. We report two cases of these tumors. The presenting symptoms were headaches in one case and seizure in the other. Radiologically, these tumors were extra-axial and unique. One tumor displayed fat accumulation, while the other had the appearance of a conventional meningioma. Microscopically, these tumors corresponded to meningothelial and transitional meningiomas containing a variable proportion of adipose tissue composed of mature adipocytes or lipoblasts. Fat content was high in one case and moderate in the other, thus explaining the radiological findings. Expression of epithelial membrane antigen and progesterone receptors was present in meningothelial, adipocyte-like, and lipoblast-like cells. These immunohistochemical results suggest that lipid accumulation in meningioma should be considered a transformation of meningothelial cells rather than a true metaplasia.

Lipomatous meningioma of the brain harboring metastatic renal-cell carcinoma: a case report

A 70-year-old woman presented with mild left hemiparesis and intermittent global headache. Magnetic resonance imaging showed a 6 x 6 x 6-cm tumor in the right frontal lobe, and abdominal computed tomography revealed a 8 x 8 x 7-cm mass lesion in the left kidney. Magnetic resonance imaging showed that the brain tumor consisted of a central hyperintense cystic component and an outer hypointense component. The patient underwent total surgical excision of the intracranial mass. Histological and immunohistochemical examination showed that the lesion was a lipomatous meningioma harboring metastatic renal-cell carcinoma. Both of these tumors are rare. The magnetic resonance imaging findings are indicative of but not specific to meningioma harboring metastatic tumor.

Lipomeningioma: case report and review of the literature

We present a case of histologically confirmed lipomeningioma, the first to our knowledge reported in Australia. A 61-year-old man presented with seizures and confusion, and was found to have a non-enhancing left extra axial temporo-parietal lesion on CT and MRI scan. On MRI, the mass lesion showed hyper-intensity on the T1 weighted images, hypo-intensity on fat suppressed T2 weighted images and no enhancement with intravenous gadolinium, indicating a mass consisting predominantly of fatty tissue. A subsequent CT also showed the mass lesion to be hypodense with Hounsfield units indicating fatty tissue. A durally based tumour with high fat content macroscopically was excised at craniotomy under ultrasound guidance. Post-operative recovery was uneventful. Histology demonstrated a meningioma with high lipid content in the form of mature adipocytes and without atypical features. While not exceedingly rare, fewer than 30 cases of lipomeningioma, lipomatous meningioma, or lipidised meningioma have been reported in the world literature.

Spontaneously T1-hyperintense lesions of the brain on MRI: a pictorial review

In this work, the brain lesions that cause spontaneously hyperintense T1 signal on MRI were studied under seven categories. The first category includes lesions with hemorrhagic components, such as infarct, encephalitis, intraparenchymal hematoma, cortical contusion, diffuse axonal injury, subarachnoid hemorrhage, subdural and epidural hematoma, intraventricular hemorrhage, vascular malformation and aneurysm, and hemorrhagic neoplasm. The second category includes protein-containing lesions, such as colloid cyst, craniopharyngioma, Rathke's cleft cyst, and atypical epidermoid. The third category includes lesions with fatty components, such as lipoma, dermoid, and lipomatous meningioma. Lesions with calcification or ossification, such as endocrine-metabolic disorder, calcified neoplasm, infection, and dural osteoma, constitute the fourth category, whereas the fifth category includes lesions with other mineral accumulation, such as acquired hepatocerebral degeneration and Wilson disease. The sixth category includes melanin-containing lesions, such as metastasis from melanoma and leptomeningeal melanosis. The last category is the miscellaneous group, which includes ectopic neurohypophysis, chronic stages of multiple sclerosis, and neurofibromatosis type I. The above-mentioned lesions are presented with their typical T1-hyperintense images, and the underlying reasons for those appearances in magnetic resonance imaging are discussed.

Meningioma associated with intraosseous lipoma

Intraosseous lipomas of the skull are quite rare and only eight cases have been reported. The lipoma in our case was different from that in others in that it showed remarkable proliferation of collagen tissue. This is the first report of meningioma occurring after removal of an intraosseous lipoma of the skull. This report concerns a rare case of a 32-year-old female who developed a huge convexity meningioma 11 years after successful removal of intraosseous lipoma of the left frontoparietal bone. The meningioma originated from the convexity where the lipoma had been, and extended intracranially to the sphenoid ridge. The patient underwent surgical exploration showing that the meningioma had invaded the frontoparietal convexity bone and was firmly attached to the coronal suture with a large dural defect. This rare coincidence suggests that proliferative changes of the intraosseous lipoma and meningeal neoplasm may be the result of the same, as yet unknown, mechanism.

Cutaneous lipomatous neurofibroma

We report a cutaneous lipomatous neurofibroma on the skin of the left-side parietal area of approximately 9 months' duration in a 67-year-old woman. The regular distribution of adipose tissue throughout the lesion suggested that fat was an integral part of the tumor, not a metaplastic or degenerative process. To our knowledge, this type of lesion has not been documented. The main differential diagnosis embraces neurocristic cutaneous hamartoma, lipoma and its variants, cutaneous meningioma, and neural nevus with fat replacement. We propose that lipomatous neurofibroma of the skin is caused by aberrant development of adipose tissue in a neurofibroma. The lesion originated as pluripotential neural crest cells after migration. This acquired lesion could arise from local stem cells. The old suggestion that neuroectoderm is capable of mesenchymal differentiation may be relevant to the histogenesis of this neoplasm.

Choristoma of the optic nerve: case report

OBJECTIVE AND IMPORTANCE

Optic nerve choristoma is a rare lesion composed of adipose tissue and smooth muscle involving the optic nerve. Few cases have been reported.

CLINICAL PRESENTATION

A 20-year-old woman presented with a history of slowly progressive visual loss in the left eye. On T1-weighted magnetic resonance imaging studies, after frequency-selective fat saturation, an optic nerve mass was detected at the level of the optic canal with signal characteristics suggesting the diagnosis of optic nerve lipoma.

INTERVENTION

At left frontotemporal craniotomy, the intracranial optic nerve appeared thin and atrophic proximally and was covered by abundant adipose tissue distally. Because no cleavage plane could be identified between the fatty lesion and the optic nerve, which appeared splayed within the adipose tissue, the nerve was resected after an intraoperative biopsy. The presence of two heterotopic mesodermal elements, a rim of adipose tissue admixed with bundles of mature smooth muscle, extending into the nerve septa, warranted a diagnosis of optic nerve choristoma.

CONCLUSION

Optic nerve choristoma is an uncommon optic nerve lesion. Even if imaging studies are highly suggestive of the diagnosis, pathological confirmation is required because of the high adipose tissue content in the majority of cases. The lesion, most likely malformative and nonneoplastic in nature, can be the cause of progressive visual loss.

The WHO classification of tumors of the nervous system

The new World Health Organization (WHO) classification of nervous system tumors, published in 2000, emerged from a 1999 international consensus conference of neuropathologists. New entities include chordoid glioma of the third ventricle, cerebellar liponeurocytoma, atypical teratoid/rhabdoid tumor, and perineurioma. Several histological variants were added, including tanycytic ependymoma, large cell medulloblastoma, and rhabdoid meningioma. The WHO grading scheme was updated and, for meningiomas, extensively revised. In recognition of the emerging role of molecular diagnostic approaches to tumor classification, genetic profiles have been emphasized, as in the distinct subtypes of glioblastoma and the already clinically useful 1p and 19q markers for oligodendroglioma and 22q/INI1 for atypical teratoid/rhabdoid tumors. In accord with the new WHO Blue Book series, the actual classification is accompanied by extensive descriptions and illustrations of clinicopathological characteristics of each tumor type, including molecular genetic features, predictive factors, and separate chapters on inherited tumor syndromes. The 2000 WHO classification of nervous system tumors aims at being used and implemented by the neuro-oncology and biomedical research communities worldwide.