Magnetic resonance imaging features of epidermoid cyst in the extremities

Background. Epidermoid cyst is a common benign soft-tissue tumor that occurs in the skin. There have been very few descriptions about the magnetic resonance (MR) images of epidermoid cysts in the extremities. MR imaging findings of epidermoid cysts may be characteristic enough to make the preoperative diagnosis possible. The purpose of this paper is to elucidate the MR imaging features of epidermoid cysts arising in the limbs.

Methods. We evaluated the MR images of five patients with an epidermoid cyst in the limbs. MR imaging and other radiological examinations were evaluated. T1-weighted (T1W), T2-weighted (T2W), and Gd-enhanced T1W images were taken in all the patients.

Results. The size of the lesion ranged from 2 to 10 cm with an average of 5.2 cm. All the tumors were located in the subcutaneous tissue with a well-circumscribed margin. On T1W MR imaging, the tumor had a slightly high signal intensity in three out of five cases and iso-signal intensity in the remaining two cases. On T2W images, they all showed high signal intensity. Irregular low signal intensity areas were noted in the tumors on both T1W and T2W images. No enhancement was observed inside the tumors.

Conclusion. Subcutaneous tumor location, well-circumscribed margin, and isosignal to slightly high signal intensity with some heterogeneity on T1W MR images and high signal intensity T2W MR images, and no enhancement are useful features for a diagnosis of epidermoid cyst of the extremity.