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.

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.

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.

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.

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.

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.

Pilomatrix Carcinoma-Rare Presentation of an Unusual Cutaneous Malignancy.

INTRODUCTION OR BACKGROUND: Pilomatrix carcinoma is a rare malignant neoplasm arising from the root of hair follicles, with only 150 cases described in the world literature. It is most commonly seen in the head and neck region. CASE PRESENTATION: We describe a case of malignant pilomatrix carcinoma in a 62-year-old gentleman presenting as a solitary globular mass over the right anterior chest wall along with a brief review of literature. DISCUSSION AND CONCLUSION: Surgical excision with a wide margin is the current standard of care for chest wall pilomatrix carcinoma and is associated with the least recurrence. Role of radiation as definitive treatment of the primary or as adjuvant therapy has not been clearly established.

Periocular pilomatrixoma in childhood: Clinical feature and differential diagnosis.

PURPOSE: 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.

Cytomorphological spectrum of pilomatricoma - A series of 28 cases.

BACKGROUND: Pilomatricoma is a benign tumour that originates in the outer sheath of the hair follicle root. The clinical diagnosis of this rare entity is often missed, possibly due to a lack of awareness. Its characteristic cytomorphological features are sheets of ghost cells, basaloid cells, calcification and foreign body giant cell reaction. However, the above features may not all be present in all cases, rendering cytological diagnosis difficult. MATERIALS AND METHODS: This retrospective study included all cases of pilomatricoma diagnosed on fine needle aspiration over a period of 4 years. The histopathological diagnosis was retrieved for the cases wherever possible. A detailed histopathological and cytological evaluation was performed for the various components-basaloid cells, ghost cells, calcified debris, foreign body giant cells, bare nuclei, neutrophils, and macrophages-and they were graded on a scale of 0 to 3+. RESULTS: The 28 cases included 8 female and 20 male patients with a mean age of 34.6 years. Most cases (22 cases; 78.6%) were located in the head and neck, with the scalp being the most common site. Twenty-five cases were cytologically diagnosed as pilomatricoma based on a variable admixture of the various components-nests of basaloid cells, ghost cells, foreign body giant cell reaction, calcified debris and viable squamous cells. However, in two cases which showed an absence of basaloid cells, a differential diagnosis of epidermal inclusion cyst was also included. Another case showed a predominance of basaloid cells with a paucity of ghost cells, so a differential diagnosis of adnexal tumour was also included. Among all the cytological parameters, sheets of ghost cells followed by nests of basaloid cells and foreign body giant cell reaction had the highest sensitivity in the cytological diagnosis of pilomatricoma. CONCLUSION: The presence of sheets of ghost cells is the most sensitive parameter for the cytological diagnosis of pilomatricoma. It is important that pilomatricoma should be considered in the differential diagnosis of subcutaneous masses, particularly in the head and neck region.

Surgical experiences in pediatric pilomatricoma: punch incision and elliptical excision.

BACKGROUND: As pilomatricoma is a common adnexal skin tumor often occurring in exposed areas, dermatologists focus on minimizing postsurgical scarring. METHODS: This retrospective study included patients aged < 19 years who underwent surgical treatment for pilomatricoma at a single university hospital from 2015 to 2021. Patient demographics, tumor characteristics, and surgical outcomes were analyzed according to the surgical methods including punch incision and elliptical excision. RESULTS: Overall, 75 patients and 79 lesions were included in the study. The mean age of the patients was 8.4 years, and 48 patients (64.0%) were females. The face was the most common site of pilomatricoma (51.9%), and within the face, the cheeks were the most common sites. No recurrence was observed in the elliptical excision group, while one case of recurrence (4.5%) was observed in the punch incision group. The mean length of the wound was 2.00 cm in the elliptical excision group, which was longer than that in the punch incision group (0.49 cm; p < .001). CONCLUSIONS: Considering that surgery is the gold standard treatment for pilomatricoma, punch incision may be useful as an alternative surgical option for pilomatricoma in children.

Commonly Misdiagnosed Facial Lesion: Pilomatricoma.

Pilomatricoma, also known as Pilamatrixoma or Malherbe's calcifying epithelioma, is a benign skin tumour with a bimodal age distribution between the paediatric and elderly age groups. Although it was previously thought to be rare, recent studies have revealed that it is quite common. Typically, pilomatricoma is diagnosed following histopathological examination of the lesion as it is frequently misdiagnosed with other types of skin pathology. In our case, the child presented with painless swelling of the left infraauricular region. The initial cytology and imaging were unable to provide a definite diagnosis. An excision biopsy was done, and a histopathological examination was suggestive of Pilomatricoma. Therefore, Pilomatricoma ought to be considered in the differential diagnosis of head and neck lesions in hopes of providing a better understanding on this pathological lesion.

Calcifying epithelioma of Malherbe - a rare localization.

Calcifying epithelioma of Malherbe, also known as pilomatricoma or pilomatrixoma, mostly arises in the matrix hair follicle. It generally affects the head and neck, upper extremities, and trunk, with the lower extremities being a rare exception. We hereby present a case of a 31-year-old male patient who presented with a small, firm, subcutaneous mass over the left malleolus, which was provisionally diagnosed as lipoma. Surgical excision was performed, and the histopathology report revealed it to be pilomatricoma of the left malleolus.

Pilomatrix Carcinoma In A 4-Year-Old Child With An Unusual Presentation.

Pilomatrix carcinoma is a rare, locally aggressive variant of pilomatrixoma with a high rate of recurrence and risk of distant metastasis. We report an unusual presentation of a pilomatrix carcinoma in a 4-year-old male child who presented with recurrent lesions on his left cheek. At the age of 1 month of life, he presented with a soft tissue swelling on his left cheek. The lesion showed a circumscribed proliferation of basaloid cells with central areas of eosinophilic ghost shadow cells and intermediate cells. Basaloid nests showed round to oval, hyperchromatic nuclei with open nuclear chromatin, prominent nucleoli and frequent mitoses but no marked nuclear pleomorphism or infiltration was identified. The lesion recurred twice at the same site. Both recurrences showed similar morphology as the primary tumour however there were extensive areas of stromal necrosis, infiltrating edges, frequent mitoses with atypical forms, and lymphovascular invasion. There was no marked nuclear pleomorphism. Morphological features favoured a diagnosis of pilomatrix carcinoma. The child is still on follow-up and no recurrence has been identified to date. Pilomatric carcinoma is rarely reported in infants. Due to its rarity, aggressive histological features may be missed.

Melanocytic matricoma with atypical features: A case of malignant melanocytic matricoma?

Melanocytic matricoma is a rarely reported, benign cutaneous adnexal neoplasm composed of epithelial cells exhibiting differentiation towards hair matrix as well as admixed, pigmented, dendritic melanocytes. The proposed malignant counterpart to melanocytic matricoma, malignant melanocytic matricoma (MMM), is even more rare. Here we report a case of a melanocytic matricoma with atypical features in a 92-year-old female with a 1.2-cm pigmented nodule on the right nasal sidewall. Histopathology revealed a well-circumscribed dermal tumor composed of atypical matrical cells with scattered aggregates of anucleate keratinocytes (ghost cells), prominent intratumoral pigment, numerous mitotic figures (88 mitosis/10 high-power field [HPF]), and intermixed dendritic melanocytes. A literature review was performed for MMM to determine if the current case fit diagnostic criteria for this entity. Including the current case, 12 cases of MMM were identified and analyzed to investigate common clinical and histopathologic features. MMM commonly occurred on the head and neck (7/12 cases) of older individuals (median age of 80) with a slight male predominance (male-to-female ratio of 3:1) and on histopathology presented as a multinodular dermal tumor composed of mitotically active (average mitotic rate of >50 mitoses/10 HPF) pleomorphic epithelial cells with foci of ghost cells. Dendritic melanocytes were found throughout the tumor lobules in all cases. Given that only two of 12 cases have exhibited locally aggressive behavior, further study is warranted to determine the true malignant potential of MMM.

A newly growing asymptomatic facial lesion.

A 23-year-old man presenting with a 1-year history of a lesion of the right cheek. We highlight this case for awareness as this tumour may mimic other benign lesions, such as pilomatrixoma or benign cysts, as it does not have any uniquely identifying clinical or dermoscopic features. Additionally, it is of concern as malignant transformation can occur and therefore surgery should be considered as both for diagnostic and therapeutic benefit.

Rare case of multiple and perforating pilomatrixomas in a young girl with lymphovascular malformation reveals a potential new disease association.

This report details the case of a girl of primary school age who was referred to our plastic surgery department with an ulcerating lesion on the nape of her neck. A firm mass was palpable in the underlying subcutaneous tissue. This lesion was accompanied by two smaller firm nodules: one in the adjacent tissue and another in the left preauricular region. Ultrasound and MRI demonstrated multiple calcified nodules confined to the subcutaneous tissue. An incisional biopsy of the ulcerating lesion confirmed a diagnosis of perforating pilomatrixoma; the lesion was subsequently excised, with no sign of recurrence at 3-month follow-up. The patient had a history of lymphovascular malformation (LVM) and a paternal history of Gardner's syndrome. Pilomatrixoma and Gardner's syndrome have a well-documented association in existing literature; aberrant Wnt/beta-catenin signalling is common to both. Recent laboratory studies suggest this pathway is also implicated in the pathogenesis of LVM.