Pilomatrixoma, also known as calcifying epithelioma of Malherbe, is a rare benign skin tumor originating from hair follicle matrix cells. It typically presents as a firm, painless subcutaneous nodule, most commonly found in the head, neck, and upper extremities. Pilomatrixoma can occasionally appear in atypical locations, posing a diagnostic challenge due to its nonspecific clinical presentation. A 43-year-old female presented with a painless, slowly enlarging mass on the lateral side of her left ankle, which had been present for approximately one year. Physical examination revealed a firm, well-circumscribed subcutaneous nodule measuring about 2 cm in diameter with normal overlying skin. An MRI of the left ankle demonstrated a well-circumscribed, subcutaneous mass with heterogeneous signal intensity, consistent with calcifications, suggesting pilomatrixoma. A fine-needle aspiration biopsy confirmed the presence of basaloid cells, shadow cells, and areas of calcification. The lesion was surgically excised, and histopathological examination validated the diagnosis of pilomatrixoma. The patient had an uneventful postoperative course, with no recurrence at the six-month follow-up. This case underscores the importance of considering pilomatrixoma in the differential diagnosis of subcutaneous nodules, even in unusual locations. A comprehensive diagnostic approach, including clinical evaluation, imaging, and histopathological examination, is essential for an accurate diagnosis. Surgical excision with clear margins is the treatment of choice, ensuring low recurrence rates and excellent patient outcomes. This report enhances the understanding of pilomatrixoma and highlights the necessity for a multimodal diagnostic strategy in managing this rare condition effectively.

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.

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UNASSIGNED: Cutaneous neoplastic disorders are often observed in small mammal pets, such as dogs, regardless of their gender.
UNASSIGNED: 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.
UNASSIGNED: 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.
UNASSIGNED: 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.
UNASSIGNED: 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.

Pilomatrixoma, also called epithelioma of Malherbe, is a benign neoplasm derived from hair follicle matrix cells. It usually presents as a solitary mass in the head and neck region and is more frequent in children and young adults, females, and the Caucasian population. Lesions equal to or greater than 5 cm are categorized as giant pilomatrixomas. We present a case of a 75-year-old female, with no known medical history, who was brought to the emergency department (ED) after falling on the street. She had a giant soft head tissue tumor, severe anemia due to intralesional chronic small hemorrhages and folates and cobalamin deficiencies, and delirant speech. The anatomopathological result of the biopsy of the tumor revealed to be a pilomatrixoma. The patient was then referred to plastic surgery, with complete excision of the tumor. After surgery, she was transferred to the psychiatric team, who assumed the delirant speech to be in the context of schizophrenia. She was discharged four months after admission.

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.
OBJECTIVE: 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.
CONCLUSIONS: The study was retrospective, and the sample size was small.
CONCLUSIONS: 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.

Pilomatricomas (PM) are benign neoplasms that arise from hair follicle matrix cells. They are one of the most frequently excised pediatric skin masses. A typical clinical presentation is a slow growing, painless, firm, superficial mass in the head and neck of a child. We present a rare presentation of PM. A preschool aged girl presented with an enlarging scalp mass following a history of minor blunt trauma to the area. Two months prior, the child sustained a ground level fall and subsequently developed a painless \"bump\" at the site of injury on the scalp. The ``bump\" was initially the size of a \"mosquito bite\" and enlarged to the size of a \"ping pong ball\". Given the rapid progression and history of trauma, there was a broad differential diagnosis. An extensive workup including sonography, computed tomography, MRI, and biopsy were performed. The final pathologic diagnosis was confirmed as pilomatricoma. An atypical presentation of PM in a child can mimic a wide variety of pathology. Our case demonstrates unusual features of rapid enlargement and preceding trauma. With the widespread use of sonography for evaluation of superficial lesions, the radiologist may be the first to suspect the diagnosis of PM. Knowledge of the typical imaging findings in PM can be valuable, especially in more unusual cases.

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.