- Author: Ian D Dickey, MD, FRCSC; Chief Editor: Harris Gellman, MD more...
Findings on plain radiography generally are not specific. The rare intraosseous lesion presents as a benign-appearing, well-circumscribed lesion. Differential diagnoses for these lesions include giant cell tumors, chordomas (when involving the spine), and chondroblastomas. Massive bony destruction may be present, especially when the lesion involves the sacrum.
Special studies to consider are those employing computed tomography (CT) scanning or magnetic resonance imaging (MRI). MRI is particularly useful (see the image below); it shows a usually round or oval mass with a moderately bright signal on T1-weighted images and a bright, heterogeneous signal on T2-weighted images. The mass is usually less than 2.5 cm in size. The lesion enhances uniformly with gadolinium contrast.
Wu et al conducted a study to determine the value of ultrasonography in the diagnosis of neurilemmoma and to determine whether the presence of a round or roundlike shape on the ultrasound image is diagnostically useful. They concluded that ultrasonography is capable of diagnosing neurilemmomas with a high degree of accuracy but that round or roundlike shape and the ratio of longitudinal maximal diameter to short maximal diameter (L/S) are of little value in identifying neurilemmomas of the limbs.
Biopsy may be needed to clearly define the tissue type. For bone lesions and for particularly large soft-tissue lesions, biopsy is prudent to ensure correct diagnosis and management. Whenever a biopsy is considered, strict biopsy guideline principles must be followed.
Lesions of the spinal cord often have a dumbbell shape; otherwise, they are fusiform in shape. They have an epineurium encapsulation, frequently with overlying vessels. The cut surface is pink or white. In very large masses, degenerative cysts, hemorrhage, or dystrophic calcification may be present.
Neurilemmomas have a well-defined, fibrous capsule. Histologically, there are two distinct regions, as follows:
Antoni A areas - These are cellular regions with predominantly benign spindle cells in many intersecting bundles; they may palisade around eosinophilic regions that are called Verocay bodies, and they are positive for S100 staining
Antoni B areas - These are much less cellular and have a background of loose connective tissue that is myxomatous in appearance
Occasionally, a more aggressive histologic appearance may predominate, but such forms usually lack mitotic figures.
Neurilemmomas are commonly classified according to the Enneking system for benign lesions, as follows:
Grade 1 - These lesions are inactive
Grade 2 - These lesions deform the surrounding tissues but are not destructive or locally aggressive
Grade 3 - These lesions are locally aggressive and may invade local tissues but do not have metastatic potential
Generally, neurilemmomas are grade 2 or 3.
Laboratory studies generally are not beneficial.
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