MR imaging findings of pilomatricomas: a radiological-pathological correlation

Background: Magnetic resonance imaging (MRI) findings of pilomatricomas have yet to be determined. Purpose: To assess the correlation between MRI and pathological findings of pilomatricomas. Material and Methods: MR images were obtained on patients with histologically proven pilomatricomas using a 1.5-T MR scanner. The images were retrospectively reviewed for size, signal intensity compared with skeletal muscles, and enhancement patterns. Furthermore, we assessed the presence of a reticular appearance, a ring-like appearance, and peritumoral fat stranding. Results: We included 11 consecutive patients with 12 histologically proven pilomatricomas (3 boys/men, 8 girls/women; age range, 4-76 years; mean age, 20 years; median age, 14 years). The tumors were located in the head and neck (n = 6), upper extremities (n = 5), and lower extremities (n = 1). The maximum tumor diameter was in the range of 7-32 mm (mean, 16.5 mm). On T2-weighted (T2W) images, five tumors showed homogeneous hypointensity, whereas six showed reticular hyperintensity and one showed cystic hyperintensity. On fat-suppressed T2W images, nine tumors showed reticular hyperintensity, eight showed ring-like hyperintensity, and five showed peritumoral fat stranding. On fat-suppressed gadolinium-enhanced T1-weighted (T1W) images, one tumor showed no enhancement, whereas three showed reticular enhancement and five showed ring-like enhancement. Histologically, edematous and fibrous stroma was observed in 10 tumors, tumor capsules in 11, and inflammatory cell infiltration of the peritumoral fat tissue in nine. Conclusion: MRI features of pilomatricomas included reticular and ring-like hyperintensities on fat-suppressed T2W images and reticular and ring-like enhancement on fat-suppressed gadolinium-enhanced T1W images.