Weekly Case

Title : Case 649

Age / Sex : 8 / M

Chief complaint: A palpable mass in right upper arm for 12 months

What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : Byeong Seong Kang, Department of Radiology, University of Ulsan College of Medicine, Ulsan University Hospital, Ulsan, Korea


Answer: Pilomatricoma



1) Plain radiograph

- Sharply demarcated subcutaneous mass with multiple calcifications

2) MRI

- Axial T2-WI: heterogeneous hypointensity with inner high signals

- Axial T1-WI: isointense relative to skeletal muscle

- Axial and coronal fat-suppressed contrast-enhanced T1-WI: intense and heterogeneous enhancement


Differential Diagnosis: Pilomatricoma / Dermoid cyst / Hemangioma


Diagnosis: Pilomatricoma



Pilomatricoma, also known as pilomatrixoma, is a benign skin tumor arising from the cortex of a hair follicle. The lesion is generally a well-demarcated, hard, mobile superficial nodule that grows slowly. It is usually encountered in patients younger than 20 years. Although all hair follicle–bearing skin surfaces can be involved, pilomatricoma most frequently occurs in the head and neck region, where the lesion is usually solitary.

Plain radiography demonstrated that pilomatricoma appeared as a solitary, sharply demarcated subcutaneous tumor with extensive sand-like or dense focal calcification. On CT, pilomatricoma has been described as well-defined subcutaneous masses with varying amounts of calcification and variable enhancement. On MRI, most of the pilomatricomas have been described as showing a homogeneous intermediate signal intensity on T1-weighted images, heterogeneous intermediate signal intensity on T2-weighted and fat-suppressed T2-weighted images, and ring-like and reticular enhancement on contrast-enhanced T1-weighted images.



  1. Bulman JC, Ulualp SO, Rajaram V, Koral K. Pilomatricoma of childhood: a common pathologic diagnosis yet a rare radiologic one. AJR Am J Roentgenol. 2016;206:182-8.

  2. Yi KM, Chen K, Wang L, Deng XJ, Zeng Y, Wang Y. Pilomatricoma (calcifying epithelioma): MDCT and MR imaging findings in 31 patients with radiological-pathological correlation. Eur J Radiol. 2018;106:92-9.

  3. Kato H, Kanematsu M, Watanabe H, Nagano A, Shu E, Seishima M, Miyazaki T. MR imaging findings of pilomatricomas: a radiological-pathological correlation. Acta Radiol. 2016;57:726-32.

Correct Answer
Total applicants 28 Correct answers 18
Name Institution
김기욱 국군수도병원, 전문의
윤유성 순천향대 부천병원, 전문의
조영민 전문의
강지희 서울대학교병원, 전문의
최형인 군의관, 전문의
이혜란 전문의
여현정 전문의
박서영 전문의
장성원 중앙보훈병원, 전공의
왕현혜 선정형외과, 전문의
신재환 국군춘천병원, 전문의
장현식 전문의
홍상협 군의관, 전문의
김성진 365병원, 전문의
손우곤 전공의
권기언 명지병원, 전공의
박선영 한림대학교 성심병원, 전문의
노윤화 전공의