RT Journal Article SR Electronic T1 Proliferating Trichilemmal Tumors: CT and MR Imaging Findings in Two Cases, One with Malignant Transformation JF American Journal of Neuroradiology JO Am. J. Neuroradiol. FD American Society of Neuroradiology SP 180 OP 183 VO 22 IS 1 A1 Hyung-Jin Kim A1 Tae Sook Kim A1 Kyung-Hee Lee A1 Young Mo Kim A1 Chang Hae Suh YR 2001 UL http://www.ajnr.org/content/22/1/180.abstract AB Summary: We report the imaging findings in two patients with proliferating trichilemmal tumors. In the first patient, the tumor arose on the lower lip, a very unusual location for this type of tumor, and showed malignant transformation with metastasis to a regional lymph node. It was seen as a poorly marginated soft-tissue mass with isointense signal on T1-weighted MR images and hyperintense signal on T2-weighted images. Large areas of high signal intensity caused by necrosis were also found within the tumor on T2-weighted images. After IV administration of contrast material, the mass showed significant enhancement, with considerable portions remaining unenhanced. In the second patient, the tumor originated from a preexisting trichilemmal cyst and occurred in the hair-bearing area of the posterior part of the neck. CT scans showed a well-encapsulated cystic mass that contained multiple speckled calcifications in a wall of variable thickness. There were several foci of smooth soft-tissue elevations from the inner wall of the mass, which corresponded histologically to proliferating portions of trichilemmal cyst.