Pilomatricoma Characterization and Management

Pilomatricoma, also known as calcifying epithelioma of Malherbe, is a benign cutaneous neoplasm arising from hair matrix cells. It predominantly affects children and young adults, presenting as a firm, slowly growing subcutaneous nodule most commonly on the head, neck or upper trunk. Histologically, lesions display basaloid cells transitioning to ghost or shadow cells with variable calcification and ossification. While usually solitary and indolent, pilomatricomas may recur after excision, and in rare instances transform into locally aggressive pilomatrix carcinoma. Accurate preoperative diagnosis remains challenging owing to clinical overlap with cysts, haemangiomas and other adnexal tumours. Imaging modalities such as high-frequency and ultra-high-frequency ultrasound, supplemented by dermoscopy, improve diagnostic accuracy by revealing characteristic features including well-demarcated hypoechoic nodules with internal echogenic foci and posterior acoustic shadowing. Molecular studies have established activating mutations in CTNNB1 leading to aberrant β-catenin expression as a hallmark of pilomatricoma, with occasional reports of FGFR2 alterations. Standard management involves complete surgical excision with clear margins to minimise recurrence. In the malignant variant, wide local excision combined with regional lymph node dissection has demonstrated the lowest recurrence rates, while the role of radiotherapy, chemotherapy or targeted therapies such as immune checkpoint inhibitors and CDK4/6 inhibitors is under exploration in refractory cases.

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Pilomatricoma Characterization and Management publication trend

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Technical terms

Pilomatricoma: Benign skin tumour derived from hair matrix cells, often calcified.

Histopathology: Microscopic examination of tissue to identify disease characteristics.

Fine-needle aspiration biopsy: Minimally invasive technique to sample cells for cytological and molecular analysis.

β-catenin: Protein involved in cell adhesion and Wnt signalling; nuclear accumulation indicates CTNNB1 activation.

Hypoechoic: Ultrasound descriptor for regions that reflect fewer sound waves, appearing darker.

Echogenic foci: Bright spots on ultrasound corresponding to calcifications.

Posterior acoustic shadowing: Ultrasound artefact where dense structures block sound waves, creating a dark shadow.

References

1. Case report: Pilomatrix carcinoma with PDL1 expression and CDKN2A aberrant. Frontiers in Immunology (2024).
2. Pilomatrix Carcinoma: Report of Two Cases of the Head and Review of the Literature. Current Oncology (2023).
3. Ultra-High-Frequency Ultrasound in the Evaluation of Paediatric Pilomatricoma Based on the Histopathologic Classification. Frontiers in Medicine (2021).
4. Novel Mutations in Pilomatrixoma, CTNNB1 p.s45F, and FGFR2 p.s252L: A Report of Three Cases Diagnosed by Fine‐Needle Aspiration Biopsy, with Review of the Literature. Case Reports in Genetics (2020).