Trichilemmal Cyst: Clinical and Sonographic Features.

OBJECTIVES: In this study, we retrospectively reviewed the clinical and sonographic features of patients with trichilemmal cysts.

METHODS: Sonographic findings of 54 cases of trichilemmal cysts were retrospectively analyzed from 50 patients, including 4 cases of proliferating trichilemmal cysts. Associated factors of internal calcification-positive cases were also evaluated.

RESULTS: The mean age of the 50 patients was 43.4 years (range, 15-80 years) and the female-to-male ratio was 1.3. Overall, 68% of the trichilemmal cysts in the 54 lesions were located in the scalp, and 15% were located in the extremities. All 54 lesions were preoperatively examined by sonography and showed well-defined, oval-shaped structures located in subcutaneous soft tissues close to the dermis. Of the 54 lesions, 72% were hypoechoic masses, 89% were heterogeneous, and 65% had internal calcification. Among the internal calcification-positive cases, the mean age of the patients was 43.4 years, and the female-to-male ratio was 0.6. Of these lesions, 83% were located in the scalp. We did not find any significant association between calcification, age, or sex (P = .993 and P = .99); however, lesions present in the scalp were significantly associated with internal calcification (P = .005). 81% of the 54 lesions displayed posterior enhancement. but the color Doppler sonography of all lesions revealed no vascularization.

CONCLUSIONS: Trichilemmal cysts should be considered to diagnose of well-defined, hypoechoic lesions with internal calcification and posterior sound enhancement in the subcutaneous soft tissues of the scalp or extremities upon sonography.