Clinical and Histopathological Perspectives of Pilomatrixoma: A Case Report

Abstract

Pilomatrixoma is a rare, benign tumor arising from hair follicle matrix cells, commonly seen in children and young adults. This case report discusses an 8-year-old male with a progressively enlarging posterior neck swelling over three months. Clinical examination revealed a mobile, subcutaneous mass. Fine-needle aspiration cytology (FNAC) suggested an adnexal tumor, characterized by cohesive clusters of basaloid cells, nucleated and anucleated squamous cells, and ghost cells. The patient underwent surgical excision of the mass, and histopathological examination confirmed a diagnosis of pilomatrixoma. Postoperative recovery was uneventful, with no signs of recurrence at the three-month follow-up. This case highlights the importance of combining clinical, cytological, and histopathological findings to accurately diagnose and manage pilomatrixoma, emphasizing the role of complete surgical excision in achieving favourable outcomes. The report adds valuable insights to the literature, aiding clinicians in recognizing and differentiating this rare tumour in paediatric patients.

Introduction

Pilomatrixoma, also referred to as calcifying epithelioma of Malherbe, is a benign skin tumour originating from hair follicle matrix cells [1]. It is most commonly seen in children and young adults, typically presenting as a firm, subcutaneous nodule. Pilomatrixomas are often located in the head and neck region, though they can appear elsewhere. Despite its benign nature, pilomatrixoma can mimic other skin neoplasms, making accurate diagnosis challenging. This report discusses the clinical presentation, diagnostic process, and management of pilomatrixoma in a paediatric patient [2].

Clinical Report

An 8-year-old male was brought to the ENT outpatient department with a chief complaint of a swelling on the posterior neck that had been progressively enlarging over the past three months [Fig. 1]. The patient did not report any pain, fever, or other systemic symptoms associated with the swelling. Upon physical examination, a firm, mobile, subcutaneous nodule was palpated in the posterior neck region. The mass measured approximately 2 cm in diameter, and the overlying skin appeared normal without any discoloration or ulceration. To further evaluate the nature of the swelling, fine-needle aspiration cytology (FNAC) was performed. The FNAC findings revealed cellular tight cohesive clusters of basaloid cells with round to ovoid nuclei, nucleated squamous cells, anucleated squamous cells, and clusters of ghost cells. These cytological features suggested a probable diagnosis of an adnexal tumour. Based on the clinical and FNAC findings, the decision was made to proceed with surgical excision of the mass. The patient was prepared for surgery under general anaesthesia. Intraoperatively, the mass was found to be well-encapsulated and was excised completely without any complications [Fig. 2]. The excised specimen was sent for histopathological examination.

Fig. 1.

Intraoperative view of the subcutaneous mass being excised from posterior neck

Fig. 2.

Excised specimen that is approximately 2 cm in diameter with firm and nodular consistency

Histopathological Examination

Gross Examination

The cut section of the excised mass showed encapsulated calcific grey-white areas with a mild gritty sensation on cutting.

Microscopic Examination

The sections revealed an encapsulated neoplasm comprising islands of basaloid cells exhibiting abrupt keratinization, along with abundant islands of ghost cells [Fig. 3]. The basaloid cells were round to elongated, hyperchromatic with inconspicuous nucleoli. Numerous foreign body giant cells and focal calcifications were noted, along with chronic lymphocytic inflammatory infiltrate and dilated congested blood vessels [Figs. 4, 5 and 6].

Fig. 3.

Depicts clusters of basaloid cells, ghosts of squamous cells along with keratinous debris (40X, Pap stain)

Fig. 4.

Depicts tightly arranged clusters of basaloid cells along with few naked nuclei (10x, Pap stain)

Fig. 5.

Depicts islands of ghost (shadow cells) and basaloid cell nests. (40x, H & E stain)

Fig. 6.

Depicts matrical keratinization and basaloid cell nests. (40x, H & E stain)

Discussion

Pilomatrixoma, first described by Malherbe and Chenantais in 1880 and later redefined by Forbis and Helwig in 1961, is a benign neoplasm originating from hair follicle matrix cells [3, 4]. It predominantly affects children and young adults, with a peak incidence in the first two decades of life. This case report of an 8-year-old male presenting with a progressively enlarging posterior neck swelling exemplifies the clinical and histopathological characteristics of pilomatrixoma.

Clinically, pilomatrixoma typically presents as a firm, mobile, and painless subcutaneous nodule, often leading to initial misdiagnosis as other benign skin lesions such as sebaceous cysts or epidermoid cysts. In this case, the patient exhibited a mobile, subcutaneous mass in the posterior neck, consistent with the typical presentation of pilomatrixoma. The differential diagnosis includes benign skin tumours like epidermoid cysts, dermoid cysts, and sebaceous cysts, as well as malignant lesions such as basal cell carcinoma and squamous cell carcinoma.

FNAC plays a crucial role in the initial evaluation of pilomatrixoma. In this case, FNAC revealed cellular tight cohesive clusters of basaloid cells, nucleated and anucleated squamous cells, and ghost cells, suggesting an adnexal tumour. However, as seen in the literature, FNAC findings can sometimes be inconclusive, necessitating histopathological confirmation. For instance, Yüce et al. (2023) highlighted the challenges in preoperative diagnosis, with many cases initially suspected to be malignant based on FNAC results [5].

Histopathological examination remains the gold standard for diagnosing pilomatrixoma. Characteristic features include basaloid cells, ghost cells, calcifications, and foreign body giant cell reactions. In this case, the histopathological analysis showed an encapsulated neoplasm with islands of basaloid cells exhibiting abrupt keratinization, abundant ghost cells, numerous foreign body giant cells, and focal calcifications. These findings are consistent with those described in the literature, where Hu et al. (2020) identified similar histopathological features in their study of 165 paediatric patients with pilomatrixoma [1].

Surgical excision is the treatment of choice for pilomatrixoma, ensuring complete removal to minimize the risk of recurrence. This approach is supported by Zhao et al. (2021), who reviewed the clinical presentation and management of pilomatrixoma in a paediatric otolaryngology practice over a 20-year period, finding that complete surgical excision typically resulted in excellent outcomes [2]. In our case, the patient underwent successful surgical excision, and the postoperative course was uneventful, with no signs of recurrence at the three-month follow-up.

The prognosis for pilomatrixoma is generally excellent, with a low recurrence rate when the tumour is entirely excised. This case aligns with the findings of Hu et al. (2020), who reported a low recurrence rate following surgical excision in their large-scale study [1]. The histopathological features, including basaloid cells, ghost cells, and calcifications, play a crucial role in distinguishing pilomatrixoma from other similar-appearing lesions.

In summary, the clinical and histopathological features of pilomatrixoma in this case report, combined with the supporting literature, emphasizes the importance of accurate diagnosis and effective surgical management. This case highlights the necessity of considering pilomatrixoma in the differential diagnosis of subcutaneous neck swellings in paediatric patients and reinforces the role of histopathological examination in confirming the diagnosis.

Conclusion

This case report highlights the importance of considering pilomatrixoma in the differential diagnosis of subcutaneous neck swellings in paediatric patients. The characteristic histopathological features are crucial for diagnosis, especially when FNAC results are suggestive but not definitive. Surgical excision is the treatment of choice and typically results in an excellent prognosis with minimal risk of recurrence. This case reinforces the necessity of thorough clinical and histopathological evaluation in the management of subcutaneous tumours in children.

Author Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by SY and SA. The first draft of the manuscript was written by SY and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Declarations

Ethical Approval

The authors did not receive support from any organization for the submitted work.

Informed Consent

Informed written consent was taken from the parents(as case was a minor) for publication.

Conflict of Interest

There is no conflict of interest.