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Objective: The purpose of this study was to analyze statistically significant diagnostic factors for pilomatricoma on the basis of ultrasonographic features., Methods: Sonographic images were retrospectively reviewed from 44 pilomatricomas, and from 43 control subjects with other subcutaneous tumors. Two radiologists determined the tumoral shape, margin, echotexture, echogenicity, posterior shadowing, posterior enhancement, hypoechoic rim, internal calcification, and vascularity., Results: The reliable diagnostic factors for pilomatricoma were hypoechogenicity (P < 0.001), heterogenicity (P < 0.05), internal calcification (P < 0.001), hypoechoic rim (P < 0.001), and posterior shadowing (P < 0.001). Scattered dots were the most common patterns of internal calcification. A combination of hypoechogenicity, heterogenicity, internal calcification of scattered-dot pattern, and a hypoechoic rim was a statistically significant difference between the two groups (P < 0.001; odds ratio, 21)., Conclusions: The features of heterogeneous echotexture, internal echogenic foci in scattered-dot pattern, and a hypoechoic rim or posterior shadowing itself could be discriminative ultrasonographic criteria for differentiating pilomatricomas from other subcutaneous tumors.

We present a case of giant calcifying epithelioma of Malherbe (pilomatrixoma) in the right upper arm of a 62-year-old man. It measured 18 x 12 x 8 cm in size, making it the largest of all the cases reported previously. CT clearly demonstrated a well-defined, subcutaneous mass with amorphous calcifications. The mass showed intermediate signal intensity on T2*-weighted MR images and slight contrast uptake on contrast-enhanced MR images. Histopathologically, this tumor showed no aggressive or malignant nature. The patient is without evidence of recurrence or metastasis 3 years following the resection.