We describe the largest reported case of pilomatrixoma in the literature. While pilomatrixomas typically present as small soft-tissue nodules of the head, neck and upper extremities, they can also present as much larger masses in atypical locations. When they present in their usual size, pilomatrixomas have typical imaging features and can be correctly diagnosed with imaging studies before histological confirmation. Their clinical and imaging diagnosis become challenging when they are very large, as in our case. A giant pilomatrixoma should also be considered for paediatric patients presenting with a large subcutaneous soft-tissue mass.

Pilomatrixoma is a benign adnexal tumor very common in pediatric age and in young adults that derives from follicular matrix cells. Although clinically it usually presents as a subcutaneous nodule of bluish color less than 3cm in size, multiple clinicopathological variants have been described in the literature. Among these we can find the giant pilomatrixoma, a rare clinical variant that reaches a size greater than or equal to 4cm and can simulate the clinical presentation of a malignant neoplasm. We report a 59-year-old man with an exophytic and ulcerated nodule in the left parotid region that was removed with the suspected diagnosis of a cutaneous squamous cell carcinoma. Histopathological analysis showed a proliferation of basaloid cells with areas of transition to ghost cells, under granulation tissue, hemorrhage, and an ulcerated epidermis. Thus, the diagnosis of giant pilomatrixoma was made. We reviewed the literature and found a total of 53 articles that report a total of 71 cases of giant pilomatrixoma. It is important to recognize this clinical subtype of pilomatrixoma because, apart from the possibility of being clinically confused with malignant lesions, the clinicopathological differential diagnosis must be made with the proliferating pilomatrixoma and pilomatrixcarcinoma.

Tetrasomy 9p is a rare genetic syndrome resulting from two additional copies of the short arm of chromosome 9. Symptoms often present in the form of congenital abnormalities including cognitive disabilities, growth retardation, abnormal earlobes, congenital heart disease, and dysmorphia of the skull and face. Current literature suggests patients with tetrasomy 9p may exhibit any combination of these symptoms or, in rare instances, none at all. Although karyotyping, chromosomal microarray, and galactose-1-phosphate uridyltransferase activity analyses are the definitive diagnostic methods used, there remains a need for more robust clinical recognition in cases of mild phenotypic expression. Herein, we present a rare case of mosaic tetrasomy 9p in a long-term survival patient with multiple and recurrent pilomatrixomas, rare benign growths more commonly found in individuals under the age of 20. To our knowledge, only two previous reports have noted concurrent tetrasomy 9p with pilomatrixomas. We are the first to identify this phenotype in an adult tetrasomy 9p patient. Dermatopathology evaluation was conducted to verify our diagnoses. Our aim is to present a unique, additional case suggesting multiple pilomatrixomas as a new defining clinical presentation of mosaic tetrasomy 9p and to review the literature underlying the genetic changes associated with this syndrome.

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.

Numerosas enfermedades cutáneas pueden presentarse como lesiones azules, el diagnóstico diferencial incluye entidades tan diferentes como las metástasis de melanoma, los angiomas, los lipomas, los quistes epidermoides, los pilomatrixoma, los nevus azules, los tumores glómicos o los hidrocistomas, como el que presentamos. La ecografía cutánea será una técnica diagnóstica complementaria de gran valor para hacer un correcto diagnostico diferencia pues cada una de estas lesiones tienen hallazgos ecográficos diferentes que orientaran el diagnóstico.

A three-year-old boy presented to our oculoplastic clinic with complaints of painless gradually increasing right upper lid mass for the last 6 months. On examination a firm mass measuring roughly 1x1 cm was present on the upper lid. The mass was non tender with fine superficial vessels running over it. A differential diagnosis of epidermoid cyst, vascular malformation, pilomatrixoma, and juvenile xanthogranuloma was considered. The patient underwent excisional biopsy of the mass. On gross examination the mass had a brain like appearance. Histopathological examination confirmed the diagnosis of molluscum contagiosum. It is rare for molluscum contagiosum to present as a solitary lid tumor. A brain like appearance of the excised mass can provide a clue towards the diagnosis

We present a rare case of a non-calcified pilomatricoma in a 67-year-old man. This tumor was extremely large in size, and its location, in the lower extremity, was very unusual. The clinical, radiographic, and histopathological features are described in detail. The role of magnetic resonance imaging (MRI) in the diagnosis of this entity is discussed. Definite internal reticulations and septations were observed. A possible explanation for this observation is that the high signal intensity reticulations may represent edematous stroma surrounding basaloid cells.

Pilomatrix carcinoma is a rare tumor that is generally not diagnosed clinically. An 80-year-old man presented with a 5-month history of rapidly growing nodule of the submandibular area. Histological examination revealed a pilomatrix carcinoma, an aggressive malignancy with metastatic potential