Pilomatricoma of Childhood: A Common Pathologic Diagnosis Yet a Rare Radiologic One.

OBJECTIVE The purposes of this study were to determine the accuracy of radiology reports in the diagnosis of pediatric pilomatricoma and to describe the characteristic imaging findings in a large cohort. MATERIALS AND METHODS Query of a pathology database between January 2009 and February 2014 yielded 623 specimens from 596 patients. Seventy-four patients (41 girls, 33 boys; mean age, 8.9 years) underwent imaging of the 80 excised lesions. Ninety imaging studies were available (58 ultrasound, 11 CT, 21 MRI). Radiology reports were reviewed. The lesions were evaluated for location, size, and imaging characteristics. RESULTS Pilomatricoma was included as an indication for two (2.2%) imaging studies. No differential diagnosis was given in 34 (37.8%) imaging reports. In the radiology reports, pilomatricoma was suggested as a possibility for 12 (13.3%) lesions. Foreign body reaction (13.3%), dermoid cyst (10.0%), and sebaceous cyst (8.9%) were other leading suggested diagnoses. In six (6.7%) reports, lesions were described as aggressive tumors. In nine (10.0%) reports additional studies were recommended. In all examinations, the lesions involved both skin and subcutaneous tissues without infiltration of the deep tissues. Hypoechoic rim (82.8%), internal reticulations (65.5%), and flow at Doppler examination (63.2%) were the most common sonographic features. MRI characteristics were enhancement (100.0%), heterogeneous T2-weighted hyperintensity with intermixed hypointensity (76.2%), T1-weighted isointensity in relation to skeletal muscle (66.7%), and absence of restricted diffusion (100.0%). CONCLUSION Although pilomatricoma is a common tumor of the skin and subcutaneous tissues, imaging is infrequently used in the diagnosis, and therefore, many radiologists are not aware of the lesion. The imaging features of pilomatricoma are consistent in all imaging modalities.