What are some clinical, CT and MRI features of schwannoma?
Schwannomas account for 4% of retroperitoneal neoplasms, are benign peripheral nerve sheath tumors, and most commonly occur in the third to sixth decades of life. Most are asymptomatic, and malignant transformation is rare, but surgical resection may be performed when they are large in size or symptomatic.
A solitary well-circumscribed enhancing mass is usually seen, eccentric in location to the parent nerve when visualized, with similar or lower attenuation relative to skeletal muscle, low-intermediate signal intensity on T1-weighted images, and heterogeneous high signal intensity on T2-weighted images. Heterogeneity is more commonly seen than with neurofibroma due to the variable presence of fat, cystic, hemorrhagic, and calcific components, potentially mimicking retroperitoneal sarcoma in its imaging appearance on CT and MRI. Occasionally, a “target” sign may be encountered on T2-weighted images, which appears as central low signal intensity and peripheral high signal intensity, although this nonspecific finding may be seen with any type of neurogenic tumor.