Pilomatrixomas: 31 years of experience in population under and over 18 years of age.

BACKGROUND: Pilomatrixoma, also known as calcifying epithelioma of Malherbe, is a benign cutaneous neoplasm that demonstrates differentiation towards the matrix portion of hair follicles. It is the most common benign cutaneous neoplasm in childhood and youth, although it can occur at any age. With a general incidence ranging from 0.001% to 0.0031% of all cutaneous tumors. There is a slight predilection for females, with a female-to-male ratio of 1.15:1. METHODS: Observational, descriptive, retrospective, and cross-sectional study conducted using the electronic database of the dermatopathology department of Dr. Manuel Gea González General Hospital, from January 1992 to July 2023. Only cases with a histopathological diagnosis of pilomatrixoma, pilomatricoma, and Malherbe's calcifying epithelioma were included. RESULTS: A total of 200 pilomatrixomas were recorded in 177 patients. The tumor predominantly affected females in the pediatric age group, with an average age of 22.98 years in the studied population. The most common location was the head (periorbital region), followed by the upper extremities and trunk. Upon separating the population into pediatric and adult groups, 111 and 89 cases were identified, respectively. CONCLUSIONS: We present a detailed study on pilomatrixomas with a comprehensive overview of the demographic, clinical, and epidemiological characteristics of this benign cutaneous neoplasm. The results revealed robust statistical data highlighting the distribution by age, gender, topography, morphology, accompanying symptoms, and frequency of clinical differential diagnoses. This study significantly contributes to the existing knowledge of pilomatrixomas and serves as a valuable reference for future research and clinical practice.

INTRODUCCIÓN: El pilomatrixoma o epitelioma calcificado de Malherbe es una neoplasia cutánea benigna que muestra diferenciación hacia la porción de la matriz de los folículos pilosos. Es la neoplasia cutánea benigna más frecuente en la infancia y la juventud, aunque puede ocurrir a cualquier edad. Tiene una incidencia general que oscila entre el 0.001% y el 0.0031% de todos los tumores cutáneos. Se reporta una ligera predilección por el sexo femenino, con una relación mujer: hombre de 1.15:1. MÉTODOS: Estudio observacional, descriptivo, retrospectivo y transversal en el que se utilizó la base de datos electrónica del departamento de dermatopatología del Hospital General Dr. Manuel Gea González, entre enero de 1992 y julio de 2023. Para la búsqueda de los casos solo se incluyeron aquellos con diagnóstico histopatológico de pilomatrixoma, pilomatricoma o epitelioma calcificado de Malherbe. RESULTADOS: Se registraron 200 pilomatrixomas en 177 pacientes. El tumor predominó en mujeres de edad pediátrica; el promedio de edad de la población estudiada fue 22.98 años. La topografía más frecuente fue la cabeza (región periorbitaria), seguida de las extremidades superiores y el tronco. Al separar la población en pediátricos y adultos, se encontraron 111 y 89 casos, respectivamente. CONCLUSIONES: Presentamos un estudio detallado sobre pilomatrixomas con una visión exhaustiva de las características demográficas, clínicas y epidemiológicas de esta neoplasia cutánea benigna. Los resultados revelaron datos estadísticos sólidos, destacando la distribución por edades, sexo, topografía, morfología, síntomas acompañantes y frecuencia de diagnósticos diferenciales clínicos. Este estudio contribuye significativamente al conocimiento existente sobre los pilomatrixomas y sirve como una referencia valiosa para futuras investigaciones y para la práctica clínica.

Pathological, histochemical, and immune-histochemical studies on some canine-skin neoplasm at Sharkia province, Egypt.

Background: Cutaneous neoplastic disorders are often observed in small mammal pets, such as dogs, regardless of their gender. Aim: An important objective of this work was to give a full account of the clinical, pathological, and immune-histochemical features of several skin tumors in dogs. Methods: This study was a case series in the hospital clinic, Faculty of Veterinary Medicine, Zagazig University, Egypt. Twenty-five dogs (14 males and 11 females) were examined clinically during the period from March 2022 to October 2023. The skin swelling was collected from affected animals and then subjected to a detailed histopathological study to record the different gross and microscopic findings and confirm the diagnosis by immunohistochemistry. Results: Skin neoplasia in dogs was exposed to various clinical signs, and the dogs' ages ranged between 3 and 11 years. Concerning tumor features, the majority of neoplasms were malignant (65.52%) more than benign (34.48%). The study revealed the presence of 29 cases of dogs showed neoplasia with different prevalence rates including squamous cell carcinoma (13.79%), mast cell tumor (6.89%), basal cell tumors (10.34%), histiocytoma (6.89%), trichoepithelioma (10.34%), transmissible venereal tumor (10.34%), trichilemmoma (3.44%), scalp paraganglioma (3.44%), pilomatricoma (10.34%), malignant melanomas (17.24%), and miscellaneous cases as fat necrosis (6.89%), in males and females dogs with different histopathological lesions and immunohistochemistry expressions for pan-cytokeratin (CK), melanocyte-differentiation antigens (S100 protein), and synaptophysin. Conclusion: Malignant melanomas (17.24%) are the extremely common cutaneous tumors diagnosed in this study. Meanwhile, benign tumors such as trichilemmoma, trichoepithelioma, pilomatricoma, and paraganglioma are less frequent in dogs.

Clinicopathological and immunohistochemical characteristics of bullous pilomatricoma: a retrospective, single-center study, and comparison with ordinary pilomatricoma.

BACKGROUND: Bullous pilomatricoma is a rare variant of pilomatricoma. As it has been published in sporadic case reports, a limited understanding of its clinicopathological characteristics restricts its effective diagnosis and treatment. OBJECTIVES: This study aimed to analyze the clinicopathological and immunohistochemical characteristics of bullous pilomatricoma to better understand the bullous transformation of pilomatricoma. METHODS: The authors conducted a retrospective study of 12 patients with bullous pilomatricoma and compared their clinical, histopathological, and immunohistochemical data with those of patients with ordinary pilomatricoma. RESULTS: Bullous pilomatricoma showed no sex preference, with a mean onset age of 31.2 years. The common sites were the upper extremities and trunk. Bullous pilomatricoma had a shorter disease duration, a larger diameter, and a greater tendency to increase in size than those of ordinary pilomatricoma. Histopathologically, bullous pilomatricoma had a shorter duration, lesser calcification, more mitotic figures, and distinct dermal features from those of ordinary pilomatricoma. Immunohistochemically, the expression of Matrix Metalloprotease (MMP)-2, MMP-9, vascular endothelial growth factor receptor-3 (VEGFR-3), and VEGF-C was elevated. STUDY LIMITATIONS: The study was retrospective, and the sample size was small. CONCLUSION: The distinctive features of bullous pilomatricoma potentially result from dermal changes associated with the release of angiogenic factors and proteolytic enzymes. This comprehensive analysis provides novel insights into the clinical features and pathogenesis of bullous pilomatricoma.

Integrating vascularity into the pattern classification of pilomatricomas on ultrasound provides a more competent approach for discriminative evaluation.

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. MATERIALS AND 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. CONCLUSION: 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.

Development of Pilomatrixoma at the Vaccination Site: A Rare Complication of COVID-19 Vaccination - A Case Report.

BACKGROUND Pilomatrixoma, pilomatricoma, or calcifying epithelioma of Malherbe, is a common benign tumor that arises from the base of the hair follicle. Pilomatrixoma has previously been reported at vaccination sites. This report is of a 65-year-old man with an 18-month history of an enlarging pilomatrixoma of the left upper arm at the vaccination site, following a first COVID-19 vaccination. CASE REPORT The case involves a 65-year-old man who developed a left shoulder mass 1.5 years ago. The mass appeared at his COVID-19 vaccine site 3 months after receiving the first dose. The mass measures 3 cm in diameter, was mobile, and exhibited no signs of infection in the physical examination. Surgical excision was performed, and pathology confirmed the mass as a pilomatrixoma, characterized by basaloid cells and keratinization. Three months after surgery, no recurrence was observed. CONCLUSIONS This report has presented an association between vaccination injection sites and pilomatrixoma aligning with previous findings. Enhanced awareness about this condition can substantially improve pilomatrixoma diagnosis accuracy and reduce unnecessary examinations and treatments. Furthermore, we recommend that, along with clinical symptoms, ultrasound imaging be considered a valuable diagnostic tool for pilomatrixoma, with histopathological results to confirm the diagnosis.

A systematic review of Pilomatrix carcinoma arising from the previous scar site of Pilomatrixoma.

Pilomatrix carcinoma is a rare tumor arising from the hair follicle matrix cells most commonly seen in the head and neck region. Also known as "calcified epithelial carcinoma of Melherbe," it was first reported in 1980 by Lopansri and Mihm. Since then till date to the best of our knowledge only around 125 cases were reported in literature, of which only 11 cases were reported to arise from histologically proven areas of previous pilomatrixoma which is the benign variant. One such case is being reported here along with the review of literature. A 50-year-old man presented with a swelling in the nape of his neck since 6 months, which was gradually increasing in size. He had a history of similar swelling at the same site 18 months back for which he underwent a surgery at a center outside. Final histopathology report was suggestive of pilomatrixoma with negative margin. Wide local excision of the tumor with 3 cm margin, placement of surgical clips followed by a primary closure was done. The final histopathology report is suggestive of pilomatrix carcinoma. The patient has no recurrence in 6 months follow-up. The differential diagnosis of pilomatrix carcinoma should be considered in cases of recurrent skin tumors. Wide local excision is the preferred treatment. Re-excision should be done in margin positive cases and cases where simple excision was done due to improper preoperative diagnosis. Due to the rarity of the disease, adjuvant treatment is not properly defined.

Diagnostic value of high-frequency ultrasound (HFUS) in evaluation of subcutaneous lesions.

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. METHOD: 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). CONCLUSION: 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.

Confused subcutaneous nodules in children: Differential diagnosis of pilomatricoma in children.

BACKGROUND: Pilomatricoma is a common but easily misdiagnosed tumor in children. AIMS: To differentiate pilomatricoma from other common subcutaneous nodules in children. PATIENTS/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.

Spatial transcriptomics of a giant pilomatricoma.

Pilomatricomas (PMs) are common benign adnexal tumors that show a predilection for the head and neck region and are characterized at the molecular level by activating mutations in the beta-catenin (CTNNB1) gene. Giant PMs are a rare histopathological variant, according to the World Health Organization, which are defined by a size greater than 4 cm and are reported to show upregulation of yes-associated protein compared to PMs of typical 1-3 cm size. We describe the case of a 67-year-old man with an 8 cm giant PM involving his temporal scalp, whose PM we characterized by 10X spatial gene expression analysis. This revealed five total transcriptomic clusters, including four distinct clusters within the giant PM, each with a unique transcriptional pattern of hair follicle-related factors, keratin gene expression, and beta-catenin pathway activity.

Childhood pilomatrixoma mimicking malignant small round blue cell tumor with positivity for CD99: Potential pitfall in cytology.

Pilomatrixoma is a relatively rare benign skin appendageal tumor, often presenting in the pediatric age group as a nodular lesion and most commonly involving the head and neck, making it amenable to primary fine needle aspiration (FNA) diagnosis. We report the clinical and histopathological findings of two cases of pilomatrixoma in children, both of which were initially misdiagnosed as small round blue cell tumors due to high cellularity and misinterpretation of the proliferating basaloid cells. Histopathology revealed basal cell proliferation and mitoses indicating that they were progressive, early lesions. The first case showed membranous positivity for CD99 which prompted a diagnosis of Ewing sarcoma. Awareness of the morphological spectrum including positivity for CD99 and careful evaluation of cell block histology could have averted the misdiagnosis. Pilomatrixoma should be included as an important differential diagnosis when faced with primitive-appearing cells on FNA, especially in children with mass lesions in the head and neck region.

Atypical Melanocytic Matricoma: A Case Report with Molecular Studies.

ABSTRACT: Melanocytic matricoma is a rare benign pilar tumor characterized by matrical differentiation and interspersed dendritic melanocytes. It may show cellular atypia and brisk mitotic activity. Histological characterization of some lesions may be difficult. In addition, because the reported cases are few and have limited follow-up, there is insufficient experience to define outcome-based criteria for malignancy. Some cases of melanocytic matricoma with more prominent atypia have been reported as malignant, but their clinical behavior is uncertain. We present a melanocytic matricoma with interspersed benign dendritic melanocytes, but moderate basaloid atypia, focally brisk mitotic activity, and atypical mitoses. Despite the apparently good delimitation of this tumor, higher magnification revealed a slightly irregular border. However, overt malignant features such as necrosis, frank asymmetry, deep infiltration, and ulceration were not present. This tumor showed a complex aberrant genomic profile with multiple whole chromosomes or chromosomal arms, losses, and duplications. The tumor mutational burden was high. A loss-of-function alteration in CDKN2A and a loss-of-function mutation in TP53 were also present. This unexpected molecular profile contrasts with the relatively bland histology of the tumor and is in line with the difficulties in microscopic differential diagnosis between melanocytic matricoma and an indolent malignant pilomatrical tumor. We suggest that molecular studies and longer follow-up periods may help to further understand and more precisely categorize borderline pilomatrical tumors with melanocytic hyperplasia.

Dermatological findings in Rubinstein-Taybi Syndrome.

Rubinstein-Taybi Syndrome is a rare congenital multisystem syndrome inherited in an autosomal dominant pattern caused by mutations in CREBBP and EP300 genes in approximately 60% and 10% respectively. These genes encode two highly evolutionarily conserved, ubiquitously expressed, and homologous lysine-acetyltransferases, that are involved in number of basic cellular activities, such as DNA repair, cell proliferation, growth, differentiation, apoptosis of cells, and tumor suppression. It is mainly characterized by global developmental delay, moderate to severe intellectual disability, postnatal retardation, microcephaly, skeletal anomalies including broad/short, angled thumbs and/or large first toes, short stature, and dysmorphic facial features. There is an increased risk to develop tumors mainly meningiomas and pilomatrixomas, without a clear genotype-phenotype correlation. Although not considered as characteristic manifestations, numerous cutaneous anomalies have also been reported in patients with this entity. Both susceptibility to the formation of keloids and pilomatricomas are the most often associated cutaneous features. In this review, we discuss the genetics, diagnosis, and clinical features in Rubinstein-Taybi Syndrome with a review of the major dermatological manifestations.

A comparative study of pilomatricoma and epidermoid cyst with ultrasound.

AIM: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Melanocytic Matricoma With Atypical Histopathological Features: A Case Report of an Extremely Rare Entity and Review of the Literature.

ABSTRACT: Melanocytic matricoma with atypical features is a rare, biphasic adnexal neoplasm displaying hair matrix differentiation, with only 3 reported cases worldwide. Generally, the lesion comprised a solid matrical and supramatrical cell proliferation, admixed with intermediate cell aggregates with sparse anucleated "shadow cells" and a prominent pigmented melanocytic hyperplasia. We report the case of a 78-year-old man with a slow-growing crusted lesion on the frontal left scalp, which in a matter of 1-2 months became a 0.6 cm well-defined, black purplish exophytic nodule. Histopathologically, the lesion presented a well-circumscribed border with a nodular dermal growth pattern, presenting different architectural features varying from benign pilomatricoma-like changes to atypical features such as moderate-to-high nuclear pleomorphism in both basaloid (matrical/supramatrical) and epidermal (keratinous) components. Strong nuclear and cytoplasmic positivity for ß-catenin was observed in matrical cells, whereas prominent cytoplasmic membrane positivity for Melan-A in dendritic melanocytes. Owing to the evidence of atypical cytological features, we propose the "atypical/borderline" category of melanocytic matricoma as part of a possible spectrum among matrical neoplasms. Pathologists should be aware of any atypical histopathological features while reporting cases due to their potential malignant transformation.

Case of Pilomatricoma After Coronavirus Disease 2019 Vaccination.

The coronavirus disease 2019 (COVID-19), which is an infection caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), spread worldwide including Japan. This COVID-19 pandemic has changed the way of life around the world. To prevent the spread of infection, several COVID-19 vaccines were rapidly developed and their vaccination is recommended. While safety and effectiveness of these vaccines have been shown, various adverse reactions occur with a certain frequency. Pilomatricoma is a benign subcutaneous tumor. Cause of pilomatricoma is unclear, however, an external insult could be a cause of part of pilomatricoma. Herein, we report a rare case of pilomatricoma after COVID-19 vaccination. Pilomatricoma should be included in the differential diagnoses of nodular lesions arising after vaccination sites, including the COVID-19 vaccine.