Arachnoidal Fibroblastoma

Arachnoidal Fibroblastoma: A Rare Central Nervous System Tumor

Introduction

Arachnoidal fibroblastoma (AFB) is a rare, benign tumor that arises from the arachnoid membrane, the innermost layer of the meninges that surrounds the brain and spinal cord. AFB was first described in 1924 by Cushing and Eisenhardt as a “meningioma-like” tumor. It is classified as a World Health Organization (WHO) Grade I tumor, indicating its low-grade malignancy.

Epidemiology

AFB accounts for less than 1% of all central nervous system (CNS) tumors. It typically affects adults in their fourth to sixth decades of life, with no significant gender predilection.

Etiology and Pathogenesis

The exact cause of AFB remains unknown. However, some studies suggest a possible association with head trauma or inflammation. The tumor is thought to originate from the arachnoid cap cells, which are responsible for maintaining the integrity of the arachnoid membrane.

Histopathology

Microscopic examination of AFB typically reveals a characteristic pattern of cellular architecture. The tumor cells are spindle-shaped or polygonal and arranged in a storiform or whorled pattern. They have bland nuclear features and minimal mitotic activity. The cytoplasm is abundant and often eosinophilic.

Clinical Manifestations

The clinical presentation of AFB depends on its location and size. The most common presenting symptoms include:

• Headache
• Seizures
• Focal neurological deficits (e.g., weakness, sensory disturbances)

Diagnosis

The diagnosis of AFB requires a comprehensive approach involving clinical history, physical examination, and imaging studies.

Imaging Studies:

• Magnetic resonance imaging (MRI): MRI is the preferred imaging modality for evaluating AFB. It typically demonstrates a well-circumscribed, extra-axial mass that enhances with contrast.
• Computed tomography (CT): CT can provide valuable information about the tumor’s size, location, and relationship to adjacent structures.

Biopsy:

In some cases, a biopsy may be necessary to confirm the diagnosis. This involves surgically removing a small sample of tissue for microscopic examination.

Differential Diagnosis

AFB must be differentiated from other CNS tumors with similar appearances, such as:

• Meningioma
• Hemangiopericytoma
• Solitary fibrous tumor

Management

The primary treatment for AFB is surgical resection. The goal of surgery is to remove the tumor completely while preserving neurological function.

Surgery:

• The surgical approach depends on the tumor’s location.
• Microscopic techniques are used to carefully separate the tumor from the surrounding brain tissue.
• Intraoperative neurophysiological monitoring may be employed to minimize the risk of neurological complications.

Radiation Therapy:

• Adjuvant radiation therapy may be considered for tumors that are incompletely resected or for patients at high risk of recurrence.

Chemotherapy:

• Chemotherapy is not typically used for AFB.

Prognosis

The prognosis of AFB is generally excellent. The vast majority of patients are cured with complete surgical resection. However, the risk of recurrence is low but not negligible.

Complications

Complications following AFB surgery may include:

• Neurological deficits (e.g., weakness, paralysis)
• Infection
• CSF leak
• Recurrence

Conclusion

Arachnoidal fibroblastoma is a rare, benign tumor of the CNS. It typically affects adults and presents with a variety of symptoms depending on its location. The diagnosis is made based on clinical findings and imaging studies, and the primary treatment is surgical resection. The prognosis for AFB is excellent, with most patients achieving a complete cure.