Pilomatrixoma: A Comprehensive Review of the Literature

Giant Pilomatrical Tumor With Broad Epidermal Components: An Example of Histological Diversity and a Potential Diagnostic Pitfall of Tumors With Pilomatrical Differentiation

ABSTRACT

The diagnosis of pilomatricoma, the most common matrical tumor, is generally straightforward; however, it exhibits diverse histology associated with various morphological stages and several clinical variants, and matrical differentiation can occur in various neoplastic diseases. A 56-year-old man was admitted to our hospital to resect an 11.0-cm skin tumor on his right shoulder. Because of its large size and surface irregularities, including multiple erosions and ulcers, cutaneous malignancies were clinically suspected. Histologically, the tumor formed numerous nodules with marked matrical differentiation in the superficial to deep dermis. Although the tumor was macroscopically asymmetrical and irregular, each nodule was microscopically round-shaped and consisted of basaloid cells without marked atypia, atypical mitoses, or lymphovascular invasion. Immunohistochemically, the tumor cells were positive for beta-catenin, LEF-1, and PHLDA-1, consistent with their pilomatrical differentiation. We diagnosed the case as a giant pilomatrical tumor with uncertain malignant potential, considering its "contradictory" features, namely, the worrisome histoarchitecture, such as the asymmetrical silhouette, but bland-looking cytological appearance. Unlike typical pilomatrical tumors, this tumor contained numerous epidermal components with features similar to those of the dermal components, resulting in a unique macroscopic and histological appearance. Our case broadens the known histological diversity of pilomatrical tumors.

Clinicopathologic analysis of trichoblastoma and comparison with nodular basal cell carcinoma

BACKGROUND

Trichoblastoma (TB) is an uncommon benign follicular tumour for which clinical data is limited since most reports originate from pathology studies.

OBJECTIVE

To describe the clinical aspects of TB.

METHODS

This is an ancillary study of a prospective multicentre cohort of 2710 clinically suspected basal cell carcinoma (BCC), including 935 nodular BCCs. Sixty-two cases were TB: they were analysed and compared to 935 nodular BCCs.

RESULTS

TB mostly occurred in females (61% vs. 43% for BCC, P<0.01) of mean age 63 years. They were located on the head and neck, mainly on the nose and forehead, in 87% of cases. The mean size was 8.1mm, 77% were<10mm (55% of BCCs, P<0.001), 8% were ulcerated (vs. 21% of BCCs, P<0.02), and 47% persisted for more than 1 year (34% of BCCs, P<0.05). Most cases had a clinical presentation similar to nodular BCC, except for 5 small, flat, white papules and 1 anfractuous plaque.

LIMITATIONS

Cases originated from a series of tumours clinically suspected as BCCs.

DISCUSSION

Some 2.6% of tumours clinically diagnosed as BCC are in fact TB. TB occurs on the head, are more frequent in women, and are smaller and of longer duration than BCC. In most cases, clinical diagnosis on clinical grounds is difficult.

Pilomatrixoma in a child mimicking a ruptured epidermal cyst clinically and histopathologically: Case report

Introduction and importance

Pilomatrixoma is a superficial benign skin tumor that originates from the matrix cells of the hair follicles. It presents more frequently during the first two decades of life and usually involves the head and neck, most often in the eyelid or eyebrow area.

Case presentation

We present a case of pilomatrixoma, which appeared at the age of 14 years with history of recurrent inflammation and discharge mimicking a ruptured epidermal cyst.

Discussion

Pilomatrixomas are often confused clinically with other benign masses, encountered in the clinical practice more frequently like dermoid cysts and epidermal inclusion cysts. The rate of accurate preoperative diagnosis ranges between 0%–30% and the correct diagnosis can be established only after excision and histopathological examination. Our case demonstrates an atypical presentation of pilomatrixoma as an epidermal inclusion cyst.

Conclusion

Ophthalmologists and ocular pathologists should be aware of the atypical presentation of pilomatrixomas to ensure early accurate diagnosis and curative treatment.

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Pilomatrixoma is a benign skin tumor with typical histopathological appearance.

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Pilomatrixoma is often confused clinically with an epidermal cyst.

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Accurate diagnosis and complete excision of pilomatrixoma is essential.

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Our case demonstrates the pitfall in diagnosing pilomatrixoma.

Huge pilomatrixomas of the scalp: A case report

Pilomatrixoma is a rare benign skin tumor differentiating toward hair matrix cells usually encountered in the head and neck region. It is most frequently appearing in the first and second decades of life. Histopathological examination is essential to make definitive diagnosis. Herein, we present an atypical case of multiple pilomatrixomas. A 69-year-old man with multiple voluminous masses over the scalp. Among the three lesions, one was clinically suspicious for malignancy, it measured 17 cm and was ulcerated in places. Histopathology confirmed the diagnosis of pilomatrixoma. The tumors were removed surgically with free margins. Otolaryngologist should be familiar with this benign tumor when evaluating soft-tissue mass in the head and neck region.

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Pilomatrixoma, is a particular and uncommon type benign subcutaneous tumors arising from the cutaneous adnexa.

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Otolaryngologist should be familiar with this benign tumor when evaluating soft-tissue mass in the head and neck region.

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Clinical follow-up of these lesions is necessary to avoid recurrence and malignant transformation.

Current Diagnosis and Treatment Options for Cutaneous Adnexal Neoplasms with Follicular Differentiation

Neoplasms derived from follicular tissue are extremely rare. Clinically, they are reported as non-symptomatic, slow-growing nodules. These lesions are mainly benign, but the malignant type can occur. Mainly middle-aged people (50-60 years of age) are affected. These carcinomas are mainly localized on the head and neck or torso. They can be locally aggressive and infiltrate surrounding tissue and metastasize to regional lymph nodes. In the minority of cases, distant metastases are diagnosed. Quick and relevant diagnosis is the basis of a treatment for all types of tumors. The patient's life expectancy depends on multiple prognostic factors, including the primary tumor size and its mitotic count. Patients should be referred to a specialized skin cancer center to receive optimal multidisciplinary treatment. This article tries to summarize all the information that is currently available about pathogenesis, diagnosis, and treatment methods of follicular tumors.

Optimal Timing of Surgical Excision in Pediatric Pilomatricoma: Association between Clinicopathological Features and Cosmetic Outcomes

Background

The treatment of choice for pilomatricomas is surgical excision; however, data for the optimal timing of treatment and cosmetic outcomes are limited.

Objective

This study aimed to investigate the optimal timing of treatment in pilomatricomas by considering clinicopathological findings and cosmetic outcomes.

Methods

Seventy-three pilomatricomas patients aged ≤15 years were retrospectively reviewed. Patients were classified into early excision (disease duration ≤12 months, group A) and delayed excision groups (disease duration >12 months, group B). Tumor characteristics, and histopathological features with evolutionary stages were assessed. Cosmetic outcomes were evaluated by the Modified Vancouver Scar Scale (MVSS), 5-point patient satisfaction score, and complication rates.

Results

Group A showed better cosmetic outcomes than group B in the MVSS (1.53±1.22 vs. 3.68±1.84), 5-point patient satisfaction score (4.08±0.89 vs. 3.18±1.01), and complication rates (11.8% vs. 36.4%), respectively (p<0.05). Secondary anetoderma, tent sign, calcification, and late regressive stage (evolutionary stage IV) were more common in group B, (p<0.05). Moreover, evolutionary stages showed a positive correlation with mean MVSS (r=0.670, p<0.05).

Conclusion

Early excision (disease duration ≤12 months) provides superior cosmetic outcomes compared to delayed procedures. Early recognition, diagnosis, and management for pediatric pilomatricomas is important to improve overall cosmetic outcomes.

Ultra-High-Frequency Ultrasound in the Evaluation of Paediatric Pilomatricoma Based on the Histopathologic Classification

Background: Pilomatricoma (PM) is one of the most common benign tumours in children. However, the inaccuracy of preoperative diagnosis and evaluation is high. Non-invasive examinations, including dermoscopy and ultrasound are helpful for diagnosing and evaluating PM. To date, ultra-high-frequency ultrasonographic features of PM have been rarely studied. Objective: We aimed to investigate the ultra-high frequency ultrasonographic features of PM in a large paediatric cohort and to determine the associations of these features with the clinical features of different histological subtypes of PM. Methods: This was a retrospective study. Patients who had both preoperative ultra-high-frequency ultrasonographic evaluation and pathological diagnosis of PM were enrolled. A series of infantile haemangiomas and cutaneous cysts during the same period were included as controls. Histological findings, including the stage, calcifying type, and ultrasonographic features of each lesion, were described. Results: A total of 133 patients with PM were included, and 147 PM lesions were analysed. The male-to-female ratio was 1:1.58, and the median age of onset was 91 (range: 10-188) months. On ultra-high-frequency ultrasonography, PM presented as heterogeneous (144/147, 98.0%), well-demarcated (143/147, 97.3%), and hypoechoic (126/147, 85.7%) tumours located between the deep dermis and subcutaneous tissue (139/147, 94.6%). The most common features were internal echogenic foci (135/147, 91.8%), hypoechoic rim (133/147, 90.5%), and posterior acoustic shadowing (94/147, 63.9%). Fourteen (9.5%) lesions were histologically categorized in the early stage, 58 (39.5%) in the fully developed stage, 65 (44.2%) in the early regressive stage and 10 (6.8%) in the late regressive stage. Three calcifying types, including scattered dots, clumps and arcs, were observed on histologic examination, which corresponded well with grey-scale imaging on ultra-high-frequency ultrasonography. Each calcifying type was significantly different in various histological stages (P = 0.001), among which scattered dots were mainly present in the early and fully developed stage and arc-shaped calcifying were present in the regressive stages. Calcification was observed in skin cysts, while there was more frequent posterior enhancement, less frequent posterior shadowing, and hypoechoic rim than PM. Haemangioma also presented as a hypoechoic tumour on grey-scale imaging. However, haemangioma was homogeneous and rarely calcifying. Conclusions: PM is a heterogeneous, well-demarcated, hypoechoic tumour located between the deep dermis and the subcutis on ultra-high-frequency ultrasonography. The most common features are internal echogenic foci (calcifying) and hypoechoic rim. Calcifying types can help in the staging of PM. Ultra-high-frequency ultrasound is a useful tool for the diagnosis and evaluation of PM.

Ossifying Pilomatrixoma of the Eyelid

Pilomatrixoma, an uncommon, usually benign cutaneous appendageal tumor, shows differentiation toward the hair follicle matrix cell. It undergoes various histopathologic stages, early on displaying epithelial and shadow cells along with granulomatous inflammation. In later stages, illustrated by this unusual case, epithelial cells disappear and are replaced by calcification and ossification. Immunohistochemistry in the current case showed transitional cell reactivity for β-catenin, probably linking the tumor to a mutation in the β-catenin gene CTNNB1. There was also transitional cell positivity for cyclin D1, a marker found in matrical cells of the human hair follicle. While pilomatrixoma occurs occasionally in the eyelid, the ossified eyelid variant in the current case is very rare, with only one preceding description in the literature.

Overview of Ultrasound Imaging Applications in Dermatology

Complete visualization of lesions is critical for the accurate diagnosis and management of dermatological diseases. Currently, the most readily available technologies used by dermatologists include dermoscopy and photography. Nevertheless, ultrasound has emerged as a useful non-invasive modality in dermatology, which can be added to the clinical examination supporting an early and more accurate diagnosis. Moreover, there are significant technological advances in recent years, such as the development of handheld devices and ultra-high frequency probes that have expanded the integration of ultrasound into daily dermatology practice. In this article, we reviewed the most common applications of ultrasound in the field of dermatology.

Pilomatricoma on 18F-fluorodeoxyglucose positron emission tomography-computed tomography: Peripheral mimic of an aggressive soft-tissue malignancy

Pilomatricoma, also known as calcifying epithelioma of Malherbe, is a rare skin tumor originating from the hair follicle matrix. We report a case of pilomatricoma in a 50-year-old woman, presenting as a rapidly growing pretibial mass. Malignant pilomatricoma is associated with potentially fatal metastases and are clinically and histologically indistinguishable from benign pilomatricoma. Thus, an ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG PET/CT) scan was requested for staging, revealing marked FDG uptake restricted to the primary lesion and no evidence of separate disease. The purpose of this report is to demonstrate the importance of PET/CT in the staging of this FDG-avid tumor; the malignancy of which is often first revealed by metastases. Our case also demonstrates that pilomatricoma should be included in the differential diagnosis of a rapidly growing peripheral soft-tissue mass; conventionally, the domain of sarcoma.

Clinical analysis and review of literature on pilomatrixoma in pediatric patients

Background

Pilomatrixoma is a benign tumor that originates from the hair follicle matrix. It usually presents as a hard, slow growing, solitary mass that can be easily misdiagnosed as other skin masses. The aim of this study was to clinically analyze a case series of pilomatrixoma in pediatric patients from Korea.

Methods

A total of 165 pediatric patients from 2011 to 2018 with a histological diagnosis of pilomatrixoma were included. A retrospective review was performed using the electronic medical records, including patient demographics, number and location of the mass, clinical and imaging presentation, and postoperative outcomes.

Results

There were 61 male and 104 female patients with 152 solitary and 13 multiple pilomatrixomas. Among solitary pilomatrixomas, the lesion commonly occurred in the head and neck (84.2%), followed by upper limbs (11.2%), lower limbs (3.3%), and trunk (1.3%). The pilomatrixoma lesion presented as the following types based on our clinical classification: mass (56.02%), pigmentation (25.31%), mixed (12.65%), ulceration (4.82%), and keloid-like (1.2%). Ultrasonography showed a high positive predictive value (95.56%). There were no specific complications observed except for two cases of recurrence.

Conclusion

Pilomatrixoma has various clinical feature presentations and commonly occurs in the head and neck. Ultrasonography is a helpful diagnostic tool. Surgical removal of the lesion is the main treatment method with a low recurrence rate.

Sonographic characteristics of pilomatricomas and their association with symptom duration

This study aimed to investigate the associations between the sonographic findings and duration of symptoms in children with pilomatricoma.This study included 86 children with 95 lesions confirmed to be pilomatricoma after pathological examination. The associations between symptom duration and sonographic observations, including the presence or absence of peritumoral hyperechogenicity, calcification, and vascularity were investigated. The internal echogenicity of each pilomatricoma was scored using a 5-point scale based on echogenic spots and calcification with posterior acoustic shadowing. The Mann-Whitney U and Kruskal-Wallis tests were used for statistical analysis.We found that the absence of peritumoral hyperechogenicity and severity of calcification were associated with increased symptom duration. Calcification, (present, 19.19 ± 18.99 months vs absent, 4.31 ± 3.24 months; P < .01) and peritumoral hyperechogenicity (present, 5.02 ± 5.80 months vs absent, 16.17 ± 18.24 months; P < .01), and grade of internal echogenicity (grade 0/1/2/3/4 = 3 months [1 patient]/4.33 ± 3.26 months [range, 1-12]/4.57 ± 3.46 months [range, 2-12]/10.89 ± 9.17 months [range, 3-28]/35.27 ± 19.16 months [range, 9-60], respectively; P = .01 and <.01) were associated with significant differences in symptom duration. There were no significant between-group differences in vascularity (6.01 ± 7.24 months; range, 1-48 vs 15.50 ± 19.12 months; range, 1-60; P = .08).Pilomatricomas with a relatively short symptom duration were more likely to exhibit peritumoral hyperechogenicity and calcification with less severe posterior acoustic shadowing compared to lesions with a longer symptom duration. These sonographic findings provided useful information that facilitated the correct and rapid diagnosis of pilomatricoma.

Distinguishing a Trichilemmal Cyst From a Pilomatricoma With Ultrasound

OBJECTIVES

To determine whether ultrasound (US) could distinguish a trichilemmal cyst from a pilomatricoma preoperatively.

METHODS

Ultrasound images of 61 pathologically proven trichilemmal cysts and 90 pathologically proven pilomatricomas were analyzed retrospectively. Two radiologists evaluated several US features. The sensitivity, specificity, Youden index, and predictive values of statistically significant US features were assessed. Parallel combined tests, serial combined tests, or both were performed to identify US features with high statistical significance.

RESULTS

Results from individual US features were not satisfactory; however, serial combined tests that included absence of complete internal echogenic foci, absence of a hypoechoic rim, absence of peritumoral hyperechogenicity, and absence of vascularity showed higher diagnostic utility. The sensitivity, specificity, Youden index, positive predictive value, and negative predictive value for correctly identifying a trichilemmal cyst were 74%, 88%, 0.62, 80%, and 83%, respectively. If 1 of these 4 US features was not a match for a trichilemmal cyst, pilomatricoma was considered.

CONCLUSIONS

It may be possible to distinguish trichilemmal cysts from pilomatricomas preoperatively using US. A combined test is superior to using any individual US feature.

Bilateral Cervical Pilomatricoma: A Diagnostic Dilemma for the Pediatric Otolaryngologist

Pilomatricomas are benign skin tumors often encountered by otolaryngologists but frequently misdiagnosed. Although they can occur at any age, they commonly present in children as a discolored superficial lesion adhered to the overlying skin. Accurate preoperative diagnosis is crucial for appropriate management, which is surgical in most cases. Here, we present bilateral pilomatricomas mimicking features of several other diagnoses in a pediatric patient. The patient was successfully treated with surgical excision. This case presented a unique diagnostic challenge, as the lesions exhibited features of several common diagnoses. In general, surgical management of pilomatricoma is curative, and recurrence is rare.

Germline Mutation of PLCD1 Contributes to Human Multiple Pilomatricomas through Protein Kinase D/Extracellular Signal-Regulated Kinase1/2 Cascade and TRPV6

Pilomatricoma, a benign skin appendage tumor, also known as calcifying epithelioma, consists of islands of epithelial cells histologically that contain anucleated cells in the center surrounded by basophilic cells and partial calcification. Sporadic pilomatricomas commonly have somatic mutations in the gene CTNNB1, but causative genes from germline and the underlying pathophysiology are unclear. In this study, we identified a germline missense variant of PLCD1 encoding PLCδ1, c.1186G>A (p.Glu396Lys), in a large Chinese family with autosomal dominant multiple pilomatricomas. Phospholipase C, a key enzyme playing critical roles in intracellular signal transduction, is essential for epidermal barrier integrity. The p.Glu396Lys variant increased the enzymatic activity of PLCδ1, leading to protein kinase C/protein kinase D/extracellular signal-regulated kinase1/2 pathway activation and TPRV6 channel closure, which not only resulted in excessive proliferation of keratinocytes in vitro and in vivo but also induced local accumulation of calcium in the pilomatricoma-like tumor that developed spontaneously in the skin of Plcd1^E396K/E396K mice. Our results implicate this p.Glu396Lys variant of PLCD1 from germline leading to gain-of-function of PLCδ1 as a causative genetic defect in familial multiple pilomatricomas.

Bowen disease with matrical differentiation: Report of an exceptional histopathologic presentation

Matrical differentiation is the distinctive feature of pilomatricoma and other purely matrical adnexal neoplasms; additionally, foci of matrical differentiation have been also described in hybrid cysts of Gardner syndrome, as well as in a wide variety of benign and malignant cutaneous tumors, including basal cell carcinoma. We report an exceptional case of Bowen disease exhibiting multiple foci of matrical differentiation, as confirmed by means of immunohistochemical studies. Several types of divergent, non-squamous differentiation have been exceptionally reported in cutaneous squamous cell carcinoma in situ (cSCCIS), including sebaceous, mucinous/glandular, poroid, tricholemmal, and neuroendocrine differentiation; matrical differentiation may be added to this list. Our findings further emphasize the undifferentiated nature of neoplastic cells in cSCCIS.

Cutaneous ultrasound and its utility in pediatric dermatology. Part I: Lumps, bumps, and inflammatory conditions

High-frequency ultrasonography represents a promising tool for pediatric dermatologists. It is a non-invasive diagnostic technique that is particularly appealing when working with children. It can be easily performed at the patient's bedside, avoiding diagnostic delays, sedation, or multiple visits. It represents a useful adjunct to clinical examination and can enhance our understanding of cutaneous diseases. Patient cooperation and limited training and experience are the main challenges for cutaneous ultrasonography in pediatric dermatology. This review describes cutaneous ultrasonography and the nuances of its use in the pediatric setting, followed by the ultrasonographic findings of cutaneous lumps, bumps, and inflammatory dermatoses commonly encountered in pediatric patients.

Pilomatrixoma of the right thigh: Sonographic-pathologic correlation in a young man

Pilomatrixoma, also known as calcifying epithelioma of Malherbe, is a histological type of benign subcutaneous tumor arising from the cutaneous adnexa. We present our experience and the characteristic findings of a pilomatrixoma of the right thigh in a young healthy man. The lesion had grown slowly in size over the past year and this was the reason for referral to the Department of Plastic Surgery. Ultrasound imaging was performed and, through the use of B-mode, color-Doppler, and elastosonography, the lesion was depicted. The patient was therefore scheduled for surgery.

Pilomatrixomas at times can pose a diagnostic challenge, especially when the location is unusual. Ultrasound and its tools, that is, color-Doppler and elastography, can assist the clinician arising the suspicion of pilomatrixoma.

An Unusual Tumor of the Ear: Pilomatricoma in a Middle-Aged Woman

Pilomatricoma is a benign tumor arising from hair follicle matrix cells, presenting as an asymptomatic, firm, slow growing, mobile, superficial skin nodule typically in children. This lesion with an atypical clinical presentation is frequently misdiagnosed as other skin lesions and even as malignant entities regardless of detailed cytological, imaging examinations; the site of occurrence is one of the keys to accurate diagnosis. Here, we present a case of pilomatrixoma involving the ear, the cymba conchae of the auricle, which is an extremely rare site for the lesion in a 52-year-old woman. The present case suggests that this benign tumor needs to be included in the differential diagnosis in patients who present with an atypical auricular lesion.