Abstract
ABSTRACTBackgroundPredominantly intraosseous meningiomas are rare entities that include true primary intraosseous meningiomas (PIM), as well as meningiomas that may show extensive bone involvement, such as en plaque meningiomas. Different hypotheses have been proposed to decipher the origin of PIMs, such as ectopic arachnoid cap cell entrapment during birth or after trauma. Surgical resection is the treatment of choice of such lesions.Case presentationWe present a case of a 65-year-old man with an enlarging mass in the parieto-occipital region that grew slowly and progressively over 13 years, following head trauma during a motor vehicle accident. One year prior to presentation, he started experiencing daily holocranial headaches and blurry vision. CT and MRI studies revealed a permeative midline calvarial lesion measuring 14 cm in greatest dimension with extensive periosteal reaction, extension into the subcutaneous soft tissues, subjacent dural thickening and intracranial extension with invasion of the superior sagittal sinus. The favored pre-operative clinical diagnosis was osteosarcoma. The abnormal calvarium was excised and histopathological examination confirmed the diagnosis of a predominantly intraosseous calvarial meningioma, WHO grade I.ConclusionsThe present case highlights the importance of histopathologic diagnosis in guiding therapeutic decisions and reiterates the necessity of considering PIM or meningiomas with extensive intraosseous component in the differential diagnosis of calvarial masses, even when imaging suggests a neoplasm with aggressive behavior, such as osteosarcoma.
Highlights
Meningiomas are slow growing, generally benign tumors of the meninges arising primarily from meningothelial arachnoid cells.[1]
Around 80% of meningiomas can be cured by surgical resection; and the most relevant prognostic factor remains the extent of resection.[1]
The Ki-67 proliferation index was estimated to be less than 5% in average; it was noted that it was higher than expected for a usual World Health Organization (WHO) grade I meningioma reaching up to 10% in the most proliferative areas
Summary
Meningiomas are slow growing, generally benign tumors of the meninges arising primarily from meningothelial arachnoid cells.[1]. We present a case of a 65-year-old man with a large intraosseous calvarial mass in the parietooccipital region that grew progressively over 13 years following head trauma (Figure 1). Histopathologic evaluation revealed a predominantly intraosseous WHO grade I meningioma with extension into subcutaneous tissue and involving the superior sagittal sinus (Figure 2). Magnetic resonance imaging (MRI) postgadolinium fat-saturated T1 sequence showed a large intraosseous mass with demonstration of intracranial extension, invasion into the superior sagittal sinus and regional dural thickening and enhancement (Figure 3). Microscopic examination of H&E-stained sections revealed a predominantly intraosseous meningioma with overall features of meningothelial-type meningioma, WHO grade I, composed of cells with eosinophilic cytoplasm and regular, ovoid nuclei with fine chromatin and small nucleoli arranged in syncytia and whorls, with extension into soft tissue (Figure 5). The gross and microscopic histopathologic features were those of an en plaque meningioma with extensive bone invasion, or possibly a primary intradiploic (intraosseous) meningioma
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