Pilomatricoma (calcifying epithelioma): MDCT and MR imaging findings in 31 patients with radiological-pathological...

To describe the radiological characteristics of pilomatricomas on multi-detector computed tomography (MDCT) and magnetic resonance imaging (MRI), and to correlate the radiological findings and pathological features.

The radiological findings of 41 pilomatricomas in 31 patients were retrospectively reviewed. The images were evaluated with emphasis on calcifications, reticular and ring-like appearances, enhancement patterns, circular target sign and peritumoral fat stranding, and correlating these with pathological features.

Of the 31 lesions evaluated by MDCT, 25(80.6%) showed different patterns of calcifications which included single in 12(38.7%) lesions and multiple in 13(41.9%) lesions, but peritumoral fat stranding was observed only in 2(6.5%) lesions. MRI scans were performed in 11 patients with 21 lesions, homogeneous and inhomogeneous hypointensities on T1-weighted (T1W) images were showed respectively in 14(66.7%) and 7(33.3%) lesions. On fat-suppressed (FS) T2-weighted (T2W) images, a ring-like hyperintensity was observed in all 21(100%) lesions, reticular hyperintensity, circular target sign, peritumoral fat stranding and secondary anetoderma were seen in 7(33.3%), 4(19%), 4(19%) and 1(4.8%) lesions, respectively; and a significant difference (P < 0.05) was found when comparing the maximum diameter of tumors with (2.3 ± 1.4 mm) and without (1.1 ± 0.3 mm) reticular hyperintensity. On contrast-enhanced T1W images, all 21(100%) lesions were found to have ring-like enhancement and 7(33.3%) of them showed reticular enhancement. The reticular and ring-like appearances on MR images respectively corresponded to the pathological edematous stroma and connective tissue capsule, and the four-layer structures of the circular target sign on FS T2W images also corresponded to pathological calcifications, shadow cells, epithelial cells and connective tissue capsule, respectively.

The characteristic radiological findings associated with pilomatricomas include different patterns of calcifications on MDCT images and ring-like, reticular appearances and circular target sign on MR images. Radiological findings are well correlated with pathological nature.