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.

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.

Pilomatricoma is a benign proliferative lesion of skin appendages that often affects the head, upper limbs, and lower limbs. The clinical appearance of the lesions is that of asymptomatic nodules measuring less than 3 cm. pathologically, these skin lesions show the presence of basaloid cell islands, eosinophilic cytoplasmic cells without nuclei, as well as hemorrhage and calcification. In this study, we present the case of an 8-year-old girl with a 5 × 5 cm skin lesion on the forearm, which lacked the typical firmness associated with pilomatricoma lesions during examination. After biopsy, the lesion was confirmed to be pilomatricoma. Furthermore, we have reviewed studies documenting pilomatricoma lesions with atypical clinical features. Based on reports of different clinical manifestations of pilomatricoma in these studies, we suggest that the clinical diagnosis of pilomatricoma should not be limited to the typical presentation of these lesions. In cases where the lesions exceed 3 cm in size, display cystic characteristics, are painful, or resemble keloids, consideration should also be given to the possibility of pilomatricoma.

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.

Pilomatrixoma (PMX), also known as calcifying epithelioma of Malherbe, is a rare benign neoplasm that arises from the hair matrix cells, commonly in the head, neck, and upper trunk regions, infrequently affecting upper and lower extremities. It has to two peaks of presentation: under 20 years of age or between 50 and 65 years of age, slightly more common in females. The neoplasm exhibits diverse clinical manifestations and is frequently subject to misdiagnosis with alternative dermatological diseases. We present an atypical case of PMX affecting the upper extremity of a 62-year-old female patient. Surgical removal of the affected tissue under local anesthesia was performed, and subsequent histopathological analysis confirmed the presence of PMX. Based on the literature search we performed, we found out that this pathology is underreported in Jordan, with only one study published describing this tumor in the maxillofacial region. Physicians should be aware of this condition and its different presentations to include it in the differential diagnosis of suspected cases to provide the appropriate management and follow-up.

In this study, a 50-year-old male patient had a painless swelling on his right forearm. The lump on the forearm started one year ago and increased in size in the last two months. The mass was 3x6 cm and had a malignant appearance on radiological imaging. The case was reported as pilomatrixoma in the histopathological examination after marginal excision. In this case report, we emphasized that pilomatrixoma is one of the diagnoses we considered in mass formations that can be seen in the upper extremity, although rare. The large mass displaying a malignant character in radiological imaging can be pilomatrixoma, and the Tru-cut biopsy before the final surgery may help diagnosis by preventing the surgeons from aggressive surgical treatment. The marginal excision shall be enough in the definitive treatment. With this study, we aimed to discuss the place of pilomatrixoma in the orthopedic literature, which is published chiefly by otolaryngology, pathology, and dermatology clinics and lacks in the orthopedic literature because it rarely involves the extremities.

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