BACKGROUND: Pilomatricoma (PM) is a cutaneous benign neoplasm derived from the hair matrix. It clinically presents as a solitary and firm nodule overlying normal epidermis and is usually not easy to be noticed at early stage. Nevertheless, when special bullous lesion occurs in a short time or even ulcerates, preoperative diagnosis by a dermatologist is often challenging especially when the pediatric patients refuse biopsy.
METHODS: We present six bullous PM cases and particularly conduct correlation analysis on the dermotoscopy and histopathology detection data. The basic information, medical history, symptoms and lesion morphology results of the patients were also provided. We found that the incidence of bullous PM was higher in females than in males, and most patients were adolescents and the predilection location seem to be consistent in the vaccine injection site. The dermatoscopic features of bullous PM reported were luminous yellow structure below, with gray-blue homogeneous areas and branched capillary. The histological features were consistent with PM, and evident epidermis bullae were above the tumor with extraordinary dilation of lymphangion in the upper dermis. The patients described in this study were Chinese patients in Han population included 4 females and 2 males, coincidentally, they are almost teen-age, respectively are 5,11,17,19,21,22 year-old.
CONCLUSIONS: This study reported and analyzed the dermotoscopy and clinical characteristics of bullous PM, dermotoscopy may guide as a rapid and reliable technique in bullous PM diagnosis.

UNASSIGNED: A 55-year-old male patient developed a mass in the left inguinal area with left lower limb swelling and first visited a local hospital 3 months earlier because of unrelieved pain. An MRI scan suggested left suprapubic branch and left acetabular bone destruction, abnormal soft tissue signals within the iliopsoas muscle of the anterior edge of the left iliac bone, and enlarged lymph nodes in the left iliac fossa and left inguinal region. The patient subsequently underwent left pelvic lesion open biopsy and inguinal lymph node resection biopsy. According to pathological reports, the left inguinal mass was considered to be a malignant tumor of cutaneous accessory origin (pilomatrix carcinoma) with extensive vitreous changes. The suprapupubis branch mass was considered to be a bone metastatic pilomatrix carcinoma. Immunohistochemistry (IHC) revealed a PDL1 combined positive score (CPS) of 8. DNA next-generation sequencing (NGS) showed CDKN2A L65Rfs*53 mutation. The patient received three cycles of gemcitabine and nedaplatin. However, the lesion progressed.
UNASSIGNED: Chemotherapy is not effective for treating pilomatrix carcinoma. PDL1 antibodies and CDK4/6 inhibitors might be treatment options for pilomatrix carcinoma.

UNASSIGNED: Rare studies have reported pilomatricoma in twins, and extremely rare cases showed lesions in the same part of the body position. We reported a case of monozygotic twins with pilomatricoma in the same location on the skin of the right upper extremity.
UNASSIGNED: Seven-year-old monozygotic twins presented to our department with a palpable, painless, and solid mass in the subcutaneous tissue of the right upper limb. A 1.5-cm diameter nodule was seen on the anterolateral aspect of the right upper extremity of the twins. The node was irregular in shape, and upon palpation, the patients reported no noticeable tenderness. Following the administration of local anesthesia, the twins underwent surgical procedure to excise the solid mass. Finally, they were diagnosed with pilomatricoma based on the clinical and histopathological features. Complete surgical resection followed by primary closure was performed. During a follow-up period of three years, there has been no recurrence observed in the twins.
UNASSIGNED: We reported a case of monozygotic twins with pilomatricoma in the same location on the skin of the right upper arm. Our findings underscore the requirement of considering genetic factors in the diagnosis and treatment of the rare conditions.

BACKGROUND: Pilomatrixoma is a benign skin neoplasm that is common in children and is often misdiagnosed. This study aimed to summarize the clinical and pathological features of pilomatrixoma in children.
METHODS: Data on demographic information, clinical and pathological features, diagnosis, and treatment of 171 patients with pilomatrixoma from Shenzhen Baoan Women\'s and Children\'s Hospital were collected and analyzed retrospectively.
RESULTS: The mean age of the patients was 5.7 (standard deviation [SD] = 3.9) years old, and there were 2 age peaks (≤1 year old, 5-11 years old) and 2 age valleys (2-4 years old, ≥12 years old). The mean disease course was 9.3 (SD = 14.1) months, 69.0%, 86.5%, and 95.3% of the patients\' disease course in 6 months, 12 months, and 24 months, respectively. The mean tumor volume was 0.6 (SD = 1.0) cm3, and 81.3% of the patients\' tumor volume ≤1.0 cm3. Tumors were distributed sequentially in the head and neck (77.2%), upper limbs (12.9%), trunk (7.6%), and lower limbs (2.3%). The correct rates of clinical and ultrasonic diagnosis were 50.9% and 38.6%, respectively. The two most common pathological features of pilomatrixoma were shadow cells (99.4%) and basaloid cells (94.7%). There were no significant differences in age, disease course, or tumor volume between the male and female patients (p > 0.05). The age and tumor volume of the patients in different body parts were significantly different (P1 = 3.10E-05 and P2 = 5.60E-05, respectively). The correlation between the disease course and tumor volume was positively significant (p ≤ 0.05). There was a significant correlation between the disease course and tumor volume in patients with tumors at upper limbs (p = 0.03).
CONCLUSIONS: The age of children with pilomatrixoma presented 2 peaks and 2 valleys. Most patients had disease courses in 24 months and with tumor volumes ≤1.0 cm3. The correct rates of clinical and ultrasonic diagnosis were relatively low. The head and neck were the most common distribution sites of pilomatrixoma, and shadow cells and basaloid cells were the most common pathological features. The tumor volume was positively correlated with disease course in patients with pilomatrixoma.

BACKGROUND: Pilomatricoma has various manifestations on color Doppler ultrasound, and a differential diagnosis is challenging. The objective of this study was to investigate which characteristics of skin lesions on color Doppler ultrasound are effective in distinguishing pilomatricoma from epidermoid cyst and dermatofibrosarcoma protuberans.
METHODS: Records of patients with pilomatricomas (n = 63), epidermoid cysts (n = 76), and dermatofibrosarcoma protuberans (n = 19) who underwent color Doppler ultrasound evaluation and surgical excision were reviewed. The anatomical distribution and color Doppler ultrasound characteristics of these lesions were analyzed. The 63 pilomatricomas were categorized into five types based on their color Doppler ultrasound characteristics, and the roles of these five types in the differential diagnosis of the aforementioned diseases were studied.
RESULTS: Pilomatricomas, epidermoid cysts, and dermatofibrosarcoma protuberans exhibited some similar characteristics. Dominantly markedly hyperechoic or hyperechoic appearance, posterior acoustic shadowing, and the presence of vascularity were the major characteristics of pilomatricomas. The pilomatricomas could be categorized into five types, with type II having a diagnostic performance of sensitivity of 65.08%, specificity of 98.95%, area under the receiver operating characteristic curve (AUC) of 0.743, positive predictive value of 97.62%, and negative predictive value of 81.03% for the diagnosis of the aforementioned skin diseases.
CONCLUSIONS: A combination of dominantly markedly hyperechoic or hyperechoic appearance, posterior acoustic shadowing, and the presence of vascularity exhibits higher diagnostic performance for the differential diagnosis of pilomatricomas, epidermoid cysts, and dermatofibrosarcoma protuberans.

BACKGROUND: It is unknown whether high-frequency ultrasound (HFUS) can evaluate invisible subcutaneous lesions. We aimed to investigate the diagnostic value of HFUS in invisible subcutaneous lesions.
METHODS: Patients with invisible subcutaneous lesions were prospectively recruited from two centres. Before undergoing biopsy or surgery, each lesion was independently evaluated by two clinicians. One provides a clinical diagnosis by only clinical examination and the other provides an integrated diagnosis by combining clinical examination and HFUS information. Diagnoses were classified as correct, wrong, and indeterminate. A total of 391 lesions from 355 patients were enrolled, including 225 epidermoid cysts, 77 lipomas, 25 pilomatrixomas, 21 haemangiomas, 19 dermatofibromas, 11 dermatofibrosarcoma protuberans (DFSP), 7 neurofibromas, and 6 leiomyomas. Using pathological results as the gold standard, diagnostic performance was compared.
RESULTS: The number of correct diagnoses increased from 185 (47.3%) by clinical examination alone to 316 (80.8%) after the addition of HFUS (P < 0.05). Meanwhile, the indeterminate diagnosis rate decreased from 143 (36.6%) to 10 (2.6%). Using HFUS, the accuracy improved significantly for epidermoid cysts (59.6% vs. 86.7%), lipomas (50.6% vs. 94.8%), pilomatrixomas (0% vs. 48.0%), haemangiomas (23.8% vs. 57.1%), and DFSPs (0% vs. 81.8%) (all p < 0.05). However, HFUS did not significantly improve the diagnostic accuracy of dermatofibromas (15.8% vs. 21.1%, p > 0.999), neurofibromas (42.9% vs. 71.4%, p = 0.625), or leiomyomas (16.7% vs. 100%, p = 0.063).
CONCLUSIONS: Combining HFUS and clinical examination can generally improve the diagnostic accuracy and decrease the indeterminacy of invisible subcutaneous lesions, especially epidermoid cysts, lipomas, pilomatrixomas, haemangiomas, and DFSPs. However, for some rare lesions, HFUS cannot provide useful information.

BACKGROUND: Pilomatricoma is a common but easily misdiagnosed tumor in children.
OBJECTIVE: To differentiate pilomatricoma from other common subcutaneous nodules in children.
METHODS: Misdiagnosed subcutaneous nodules in four children were recorded.
RESULTS: A red mass on a 7-year-old boy\'s head which had been misdiagnosed pyogenic granuloma was proved to be pilomatricoma. A red mass on an 8-month-old boy\'s face which had been misdiagnosed infantile hemangioma also turned to be pilomotricoma. A red mass on a 21-month-old girl\'s breast, which had been misdiagnosed pilomatricoma, was proved to be infantile myofibroma. A subcutaneous nodule under a 13-month-old girl\'s armpit, which had been misdiagnosed pilomatricoma, turned to be BCG-associated lymphadenitis.
CONCLUSIONS: When a child with a subcutaneous nodule attends, pilomatricoma, vascular tumors, fibrous tumors, and BCG-associated lymphadenitis should be considered.

To explore and compare the ultrasonic (US) features of pilomatricoma (PM) and epidermoid cyst (EC) in the differential diagnosis and improve the accuracy of US diagnosis of PM.
Three hundred and nine patients who underwent US examination before surgery with a histopathological diagnosis of PM or EC after surgery were analysed retrospectively. The patients were categorised into the training and validation sets according to the inspection times. Univariate analysis was undertaken on the US and clinical features of PM and statistically significant variables (p<0.05) were included in the multivariate logistic regression model to establish a diagnostic model.
The results demonstrated that the multivariate logistic regression model for PM was statistically significant (p<0.001). The risk factors included posterior echo attenuation and hypoechoic halos (odds ratio [OR] = 9.277, 10.254) and the protective factors included age, diameter thickness, and posterior echo enhancement (OR=0.936, 0.302, 0.156). The performance of the diagnostic model was tested using the training set (area under the receiver operating characteristic curve [AUC] = 0.974, 95% confidence interval [CI] = 0.955-0.994) and the validation set (AUC = 0.967, 95% CI = 0.926-1.000), which demonstrated good discriminant ability.
The diagnostic accuracy for PM was higher than that for EC when the nodule is characterised by posterior echo attenuation, hypoechoic halos, smaller thickness, and younger age. The US diagnostic model developed may be used to guide the diagnosis of PM.

OBJECTIVE: To explore the clinical characteristics, imaging features, and differential diagnosis of periocular pilomatrixoma in children and provide evidence for clinical diagnosis and treatment.
METHODS: Retrospective analysis of the clinical characteristics, preliminary diagnosis, imaging features, treatment, and follow-up of the cases of pediatric periocular pilomatrixoma treated at our hospital.
RESULTS: A total of 59 patients from 4 months to 13 years of age (median age 4 years) were collected; 18 cases (30.51%) were misdiagnosed as other diseases in preliminary diagnoses. Seven cases underwent computed tomography (CT) examination, with CT value ranging from 63.4 Hounsfield Units (HU) to 952.0 HU (median value 151.0 HU). Six cases underwent magnetic resonance imaging (MRI) examination; two patients underwent an enhanced scan. The results showed that the rim of the lesion was enhanced, but the contents were not enhanced. All patients underwent surgical treatment. No recurrence was found from 1 month to 5 years of follow-up.
CONCLUSIONS: Periocular pilomatrixoma is a relatively common tumor in children, which can easily be misdiagnosed clinically as other diseases, such as sebaceous and dermoid cysts. Although not generally recommended, CT can be of significant value in the diagnosis of pilomatrixoma. MRI is of little value in the diagnosis of this disease. If CT images show high or density, the possibility of pilomatrixoma should be considered.

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