Findings: An avoid mass is present in the intercompartment fat plane between the adductor and quadriceps femoris muscles along the expected course of the femoral neurovascular structures. The mass is homogeneously isotense with muscle on the T1-weighted sagittal image (A). On the T2 weighted axial image (B) the mass has a target appearance with a hyperintense rim and central area of decreased signal intensity.

Diagnosis: Neurofibroma.

Discussion: The target appearance of a soft tissue mass on T2 weighted images is reported to be unique to neurofibromas. The appearance reflects the histology with dense collagen and fibrous tissue centrally and myxoid material in the periphery. While areas of low signal on T2 weighted images may be seen within schwannomas this characteristic target appearance has not been reported. No other soft tissue masses exhibit this imaging characteristic.

Reference:
Cerofolini E, Landi A, DeSantis G, Maiorana A, Canossi G, Romagnoli R.
MR of Benign Peripheral Nerve Sheath Tumors. J Comput Assist Tomogr
1991;15:593-597.

Suh JS, Abenoza P, Galloway HR, Everson LI, Griffiths HJ. Peripheral
(Extracranial) Nerve Tumors: Correlation of MR Imaging and Histologic
Findings. Radiology 1992; 183:341-346.

Varma DGK, Moulopooulos A, Sara AS, et al. MR Imaging of Extracranial
Nerve Sheath Tumors. J Comput Assist Tomogr 1992; 16:448-453.

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