MR imaging of thoracic neurilemmomas

Magnetic resonance (MR) imaging features of 15 thoracic neurilemmomas were analyzed. Morphologically, five tumor patterns could be identified on MR imaging including: inhomogeneous masses (n = 8), thick-walled multiloculated masses (n = 2), thick-walled central cystic masses (n = 2), homogeneous cystic masses (n = 2) and a target pattern mass (n = 1). The signal characterization of thoracic neurilemmomas was variable, usually brighter on T2-weighted images, hyper- to hypo-intense on T1-weighted images and always enhancing. Histopathologically, the inhomogeneous masses were characterized by irregular distribution of hypercellular Antoni A and hypocellular Antoni B tissues with variable degrees of cystic, hemorrhagic, myxoid and hyaline degenerative changes. Enlargement of the cystic areas led to the development of thick-walled multiloculated masses while confluence of these cystic areas produced a central cystic pattern. Extensive myxoid or hyaline degeneration yielded homogeneous cystic tumors. Peripheral fibrinous changes and central Antoni B stroma contributed to a target pattern. Appreciation of the protean MR manifestations and understanding of the underlying histopathological changes of thoracic neurilemmomas are helpful in the diagnosis of this tumor.