Objective To explore the clinical manifestation, ultrasonic, dermoscopic and histopathological features of pilomatricoma and to improve the correct rate of preoperative diagnosis.

Methods The clinical data of patients who underwent surgery for skin lesions that were pathologically confirmed as pilomatricoma in Zhongshan Hospital, Fudan University (Xiamen Branch) from January 2018 to March 2022 were retrospectively collected.

Results A total of 77 tumors in 75 patients (39 female and 36 male) were analyzed. The age of the patients was 4-79 years old, and with a mean age of (32.2±17.2) years old. The tumor mostly presented as firm subcutaneous nodule with predilection site on the head, face and neck (62.3%). Patients mostly presented with single tumor except 2 patients were noted with multiple tumors (2 lesions). Only 14.3% lesions (11/77) were preoperatively diagnosed as pilomatricoma. Soft-tissue ultrasound was performed on 34 lesions, 11(32.4%) of which were compatible with piolmatricoma diagnosis. Ultrasonography revealed that lesions mostly located in the subcutaneous layer (33, 97.1%), oval or oblate, well-defined, heterogeneous hypoechoic masses, with or without punctate, patchy, or band calcification. Most of the lesions did not have hypoechoic halos or posterior acoustic shadows, and there were or no color blood flow signals around or inside. Dermoscopy were performed on 9 lesions, which revealed vascular structure in 7 (77.8%) lesions, included red homogeneous structure (55.6%), irregular linear vascular structure (11.1%), punctate vascular structure (22.2%); white homogeneous structure in 2 (22.2%) lesions and grey blue unstructured area in 3 (33.3%) lesions. The histopathological manifestations were clear-cut dermis or subcutaneous nodules formed by shadow cells and basophils. The microscopic manifestations varied at different stages of the disease. The longer the course of the disease, the more shadow cells observed.

Conclusions The clinical manifestations of pilomatricoma varied and clinical misdiagnosis was common. The clinicians and ultrasound doctors need to improve the knowledge of the disease.