I. Overview
Meningeal sarcoma is a general term for a group of malignant tumors originating from the mesenchymal tissue of the meninges, which are mesenchymal non-meningeal epithelial tumors, accounting for about 0.7-3% of central nervous system tumors. Meningeal sarcoma is more common in infants and young children. The tumor is soft and brittle, infiltrates and grows with high malignancy, and can directly invade the skull, sinus and brain parenchyma through meninges or have distant metastasis.
Classification
Primary meningeal sarcoma originates from the malignant change of meningeal mesenchymal cells.
2. Secondary meningeal sarcoma comes from malignant transformation of benign meningioma, and malignant transformation of hemangioblastoma is more common.
Histological origin and pathological type
Meningeal sarcoma is not an independent type of tumor, but a general term for a group of malignant tumors originating from meningeal mesenchymal tissue, mainly including the following tumors.
1. fibrosarcoma
2. smooth muscle sarcoma
3. rhabdomyosarcoma
4. Chondrosarcoma
5. osteosarcoma
6.Malignant fibrous histiocytoma
7.Liposarcoma
8.Angiosarcoma
9. Primary meningeal sarcoma refers to a sarcoma-like disease consisting of malignant spindle cells and mesenchymal tumor cells that diffusely invade the soft meninges and lack local masses.
IV. Clinical manifestations
1. Patient characteristics Meningeal sarcoma can occur at any age, but is more common in children before the age of 10 years, with no significant gender differences, especially in sarcomas with a muscular component. Malignant fibrous histiocytoma and fibrosarcoma are more common in adults.
Some patients have a history of trauma, craniotomy, non-radical surgery for meningioma, radiotherapy, chemotherapy or AIDS, as well as a history of neurofibromatosis, Fi-Fraumeni syndrome and soft tissue sarcoma.
The course of the disease is generally short, except for a few cases of prolonged disease, and rarely exceeds 1 year, and may even present as acute or subacute encephalitis.
Clinical manifestations include headache, epilepsy, psychiatric symptoms, neurological dysfunction and hydrocephalus, etc. Continuous and severe headache, frequent vomiting and significant neck strength are the clinical features of the disease.
In addition to the neurological localization signs related to the lesion site, optic papilloedema and neck resistance are common, and painless masses can be found due to tumor invasion of skull and scalp.
V. Imaging examination
Meningeal sarcoma lacks specific imaging features.
1. Head CT shows single or multiple foci with uneven enhancement, cystic changes and bone erosion and destruction are visible, tumor calcification and skull hyperplasia are rare.
2. Head MRI shows low signal in T1-weighted image and high signal in T2-weighted image, except for liposarcoma which has high signal in both T1- and T2-weighted images, most meningeal sarcomas have low signal in T1-weighted image and high signal in T2-weighted image.
VI. Diagnosis
Children before 10 years of age or patients with a history of the above-mentioned related diseases, with a short course, obvious symptoms of cranial hypertension, persistent and severe headache, frequent vomiting and significant neck strength similar to the manifestations of acute or subacute encephalitis, especially when optic papillar edema and subscalp masses are found on examination, accompanied by systemic manifestations of malignancy such as anemia, generalized wasting and unexplained fever, need to consider the possibility of this disease.
If CT and MRI reveal extra-axial intracranial lesions with inhomogeneous enhancement and cystic changes, accompanied by severe peritumoral edema and cranial bone destruction, this disease should be considered as a possibility.
The final diagnosis depends on the postoperative pathological diagnosis, especially PAS staining, immunohistochemistry and even electron microscopy, to confirm the diagnosis and differentiate the various types of meningeal sarcoma.
Differential diagnosis
1. Benign meningioma has a long course and progresses slowly, mostly manifested by long-term headache, adult epilepsy, psychiatric changes, cranial confined mass, and fundus optic papilledema. The cranial X-ray is mostly osteophytic; CT and MRI are mostly smooth-edged and regular round-like masses with uniform enhancement without obvious cystic changes or necrotic areas; calcification is common; unless venous return is affected, peritumoral edema is mostly mild to severe.
Malignant meningioma is difficult to differentiate from malignant meningioma preoperatively based on the patient’s clinical presentation and imaging, and often requires postoperative pathologic diagnosis, especially PAS staining, immunohistochemistry and even electron microscopy to differentiate from it, and is used to distinguish between various types of meningeal sarcomas.
Bacterial meningitis is easily confused with bacterial meningitis because of the short course and rapid progression of meningeal sarcoma, which may present with persistent and severe headache, frequent vomiting and significant neck strength similar to the manifestations of acute or subacute encephalitis. Cerebrospinal fluid examination after careful assessment of the risk of lumbar puncture can help differentiate the two: centrifugation of cerebrospinal fluid in patients with meningeal sarcoma may reveal tumor cells; in patients with bacterial meningitis, cerebrospinal fluid changes such as increased leukocytes, high protein content, and decreased sugar and chloride, and bacterial culture may identify the causative organism.
4. primary hydrocephalus neuroimaging tumor occupancy effect and other changes, vomiting, neck strength and other symptoms can disappear after lumbar puncture and drainage of cerebrospinal fluid (while the above symptoms are difficult to improve significantly or disappear due to the infiltration of tumor into meninges and nerve roots), and tumor cells cannot be found by centrifugal examination of cerebrospinal fluid.
5. Meningeal implantation of other malignant tumors (such as hemangioepithelial cell tumor, malignant neuroectodermal tumor, gliosarcoma, etc.) needs to be confirmed with the patient’s history of primary tumor and postoperative pathology.
VIII. Treatment
1. Microscopic radical tumor resection is the preferred treatment method, striving to achieve Simpson grade I resection, i.e., including the affected dura and skull together, and if the situation allows, the peripheral dura can be further expanded.
At present, radiotherapy is mostly advocated after surgery to delay recurrence, and chemotherapy is not effective. In recent years, it has been advocated to combine chemotherapy with lomustine (CCNU) and teniposide (VM-26), and to consider intrathecal application of chemotherapeutic drugs such as methotrexate (MTX) and cytarabine if necessary, and to supplement with dexamethasone to reduce chemical meningitis.
3. For patients with recurrence, a second surgery should be performed as soon as the patient’s systemic condition allows. It is recommended to remove all the dura and affected bones within 4cm of the tumor, and postoperative radiotherapy is also recommended.
4. For patients with severe hydrocephalus, lateral ventriculoperitoneal shunt can be attempted. Although there are risks of intrinsic tumor implantation and shunt blockage, it is still a desirable method to relieve cranial hypertension and prolong the life of patients sometimes.
IX. Prognosis
There is no very effective treatment yet, and it is difficult to remove the tumor completely by surgery, and it is easy to recur after surgery, and extracranial metastasis can occur. The overall prognosis is poor, and the survival of patients is short, with an average survival of no more than 2 years and a low 5-year survival rate.