Development of fat within a meningioma

Extra-axial brain tumors

Extra-axial brain tumors are the most common adult intracranial neoplasms and encompass a broad spectrum of pathologic subtypes. Meningiomas are the most common extra-axial brain tumor (approximately one-third of all intracranial neoplasms) and typically present as slowly growing dural-based masses. Benign meningiomas are very common, and may occasionally be difficult to differentiate from more aggressive subtypes (i.e., atypical or malignant varieties) or other dural-based masses with more aggressive biologic behavior (e.g., hemangiopericytoma or dural-based metastases). Many neoplasms that typically affect the brain parenchyma (intra-axial), such as gliomas, may also present with primary or secondary extra-axial involvement. This chapter provides a general and concise overview of the common types of extra-axial tumors and their typical imaging features.

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.

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.

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.

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

We report 18 cases of lipomatous meningioma occurring in patients aged 14 to 79, most being females (72%). Sixteen were supratentorial and 2 involved the spinal meninges. Follow-up ranged from 1 to 120 months. Fifteen patients were cured with surgery alone and 3 (17%) experienced a recurrence at 7, 8 and 24 months. Of these, one died with disease 4 years after resection of the primary lesion. Histologically, 12 tumors were meningothelial, 3 transitional, 2 showed myxoid stromal changes and 1 was microcystic. The 2 spinal tumors were atypical. The proportion of fatty cells ranged from 10 to 90%. These resembled mature adipocytes or less commonly lipoblasts. Xanthomatous meningothelial cells were also noted in 6 tumors (30%). Both conventional meningothelial as well as lipid-laden cells exhibited epithelial membrane antigen immunoreactivity. In addition, occasional cells resembling mature adipocytes showed reactivity for S-100 protein. Ultrastructurally, lipidization of neoplastic cells varied from intracytoplasmic lipid droplets to a single massive globule. Moreover, lipid-laden meningothelial cells featured interdigitating cell membranes and well-formed desmosomes. Lipid droplets were not membrane-bound. In that metaplasia denotes differentiation of one mature cell type to another, lipid accumulation in meningiomas cannot be considered true metaplasia since their lipid-laden cells retain the immunophenotype and ultrastructural features of meningothelium. We suggest that this distinctive subset of meningiomas be termed "lipidized meningiomas" rather than being included in the metaplastic category.

Imaging features of posterior fossa neoplasms in children and adults

Masses in the posterior fossa may be divided into extra-axial and intra-axial lesions. Because of its multiplanar capabilities, improved soft-tissue resolution and contrast, and the absence of scanning artifacts related to the osseous skull base, which are frequently present on CT, MRI is the imaging modality of choice in evaluating lesions arising in the posterior fossa. It is the best means of critically localizing lesions and determining the extent of disease. Analysis of the signal characteristics of a lesion on multiple different imaging sequences (T1-weighted, T2-weighted, and enhanced images) may provide information about the tissue constituents within a mass/neoplasm, such as the presence of cellularity, necrosis, and hemorrhage. MRI is also useful in guiding localization for brain tumor biopsies and assists in planning radiation therapy. However, CT also plays an important role. CT is frequently the first imaging study performed in patients with posterior fossa masses who often present with nausea, vomitting, ataxia, and other signs of increased intracranial pressure. It is a quick, available, and relatively inexpensive study to assess neurological emergencies including hydrocephalus, hemorrhage, and herniation syndromes. In addition, it frequently provides complimentary information, such as the presence of calcification or bony remodeling (osteosclerosis or osteolysis), which MRI is less sensitive in detecting.