Multimodal Ultrasound Evaluation of Bullous Pilomatricoma: A Subcutaneous Mass With Progressive Growth in the Upper Arm.

Bullous pilomatricoma (BP), a rare variant of pilomatricoma, accounts for approximately 2% of pilomatricoma cases. We present the case of a 19-year-old male with a painless, blister-like lesion on the left upper arm, diagnosed as BP based on histopathological examination. This report emphasizes the multimodal ultrasound features of BP, incorporating grayscale ultrasound, color Doppler flow imaging (CDFI), and shear wave elastography (SWE). Notably, to our knowledge, this is the first case to detail the SWE characteristics of BP, demonstrating a mean stiffness value of 52.0 kPa. Our findings indicate that BP can exhibit deceptively high stiffness on elastography, unlike other benign skin masses that appear less stiff, highlighting the importance of integrating multiple sonographic techniques for accurate preoperative assessment of skin tumors.