Distinguishing a Trichilemmal Cyst From a Pilomatricoma With Ultrasound

Post-traumatic pilomatricoma presenting as rapidly enlarging pediatric scalp mass

Pilomatricomas (PM) are benign neoplasms that arise from hair follicle matrix cells. They are one of the most frequently excised pediatric skin masses. A typical clinical presentation is a slow growing, painless, firm, superficial mass in the head and neck of a child. We present a rare presentation of PM. A preschool aged girl presented with an enlarging scalp mass following a history of minor blunt trauma to the area. Two months prior, the child sustained a ground level fall and subsequently developed a painless "bump" at the site of injury on the scalp. The ``bump" was initially the size of a "mosquito bite" and enlarged to the size of a "ping pong ball". Given the rapid progression and history of trauma, there was a broad differential diagnosis. An extensive workup including sonography, computed tomography, MRI, and biopsy were performed. The final pathologic diagnosis was confirmed as pilomatricoma. An atypical presentation of PM in a child can mimic a wide variety of pathology. Our case demonstrates unusual features of rapid enlargement and preceding trauma. With the widespread use of sonography for evaluation of superficial lesions, the radiologist may be the first to suspect the diagnosis of PM. Knowledge of the typical imaging findings in PM can be valuable, especially in more unusual cases.

Pilomatrixoma and its Imitators

Introduction: Pilomatrixomas are benign neoplasms derived from hair follicle matrix cells. They are among the most common soft tissue head and neck tumors of childhood. Pilomatrixomas are typically isolated, slow-growing, firm, nontender masses that are adherent to the epidermis but mobile in the subcutaneous plane. This clinical presentation is so characteristic that many experienced surgeons will excise suspected pilomatrixomas without prior imaging. We reviewed the results of this approach to determine whether physical examination alone differentiates pilomatrixomas from other similar soft tissue lesions of the pediatric head and neck. Methods: Computerized review of all pilomatrixomas over a 20-year period in a single academic pediatric otolaryngology practice. Results: 18 patients presented to our pediatric otolaryngology practice between 2001 and 2021 with historical and physical findings consistent with pilomatrixoma. Of the 18 patients, 7 were male and 11 were female. Ages ranged from 1.5 to 14 years, with a mean of 7.5 years. Most of the lesions (12) were located in the head and face, while the rest (6) were found in the neck. All patients were treated with complete surgical excision. Pathology confirmed pilomatrixoma in 15 patients. The remaining 3 children were found to have an epidermal inclusion cyst, a ruptured trichilemmal cyst, and a giant molluscum contagiosum lesion, respectively. One additional patient presented with a small lesion of the auricular helix that was thought to be a dermoid cyst, but proved to be a pilomatrixoma on histologic examination. Discussion: As pilomatrixomas are common and have a very characteristic presentation, surgical excision without prior diagnostic imaging will lead to correct treatment in the majority of cases. High resolution ultrasonography can help to confirm the diagnosis preoperatively, but is not definitive in large case series. Most of the cystic lesions that imitate pilomatrixoma will ultimately require surgical excision.

Integrating vascularity into the pattern classification of pilomatricomas on ultrasound provides a more competent approach for discriminative evaluation

BACKGROUND

Pilomatricoma has various manifestations on color Doppler ultrasound, and a differential diagnosis is challenging. The objective of this study was to investigate which characteristics of skin lesions on color Doppler ultrasound are effective in distinguishing pilomatricoma from epidermoid cyst and dermatofibrosarcoma protuberans.

MATERIALS AND METHODS

Records of patients with pilomatricomas (n = 63), epidermoid cysts (n = 76), and dermatofibrosarcoma protuberans (n = 19) who underwent color Doppler ultrasound evaluation and surgical excision were reviewed. The anatomical distribution and color Doppler ultrasound characteristics of these lesions were analyzed. The 63 pilomatricomas were categorized into five types based on their color Doppler ultrasound characteristics, and the roles of these five types in the differential diagnosis of the aforementioned diseases were studied.

RESULTS

Pilomatricomas, epidermoid cysts, and dermatofibrosarcoma protuberans exhibited some similar characteristics. Dominantly markedly hyperechoic or hyperechoic appearance, posterior acoustic shadowing, and the presence of vascularity were the major characteristics of pilomatricomas. The pilomatricomas could be categorized into five types, with type II having a diagnostic performance of sensitivity of 65.08%, specificity of 98.95%, area under the receiver operating characteristic curve (AUC) of 0.743, positive predictive value of 97.62%, and negative predictive value of 81.03% for the diagnosis of the aforementioned skin diseases.

CONCLUSION

A combination of dominantly markedly hyperechoic or hyperechoic appearance, posterior acoustic shadowing, and the presence of vascularity exhibits higher diagnostic performance for the differential diagnosis of pilomatricomas, epidermoid cysts, and dermatofibrosarcoma protuberans.

Concurrent Occurrence of Trichilemmal Cyst and Nevus of Ota: Case Series

Nevus of Ota or congenital oculodermal melanosis (ODM) is characterized by brown or blue/gray asymptomatic brown or blue/gray flat lesions of the skin, mucosae, episcleral/sclera, and uvea, which are located near the trigeminal nerve's ophthalmic and mandibular branches. The main ophthalmic complications are glaucoma and predisposition to uveal melanoma. "trichilemmal cyst" is also known as "wen" "pilar cyst" or " isthmus catagen cyst". It occurs in the scalp and mimics sebaceous cysts clinically. The swelling appears smooth in outline and is filled with cytokeratin. An unusual case of a 32-year-old male with both trichilemmal cyst and nevus of Ota, a 27-year-old female, and a 47-year-old male with nevus of Ota is discussed here.

The Value of Ultrasound for Differentiating Trichilemmal Cysts From Epidermoid Cysts

OBJECTIVES

This study was aimed to evaluate the diagnostic performance of ultrasound (US) in differentiating trichilemmal cysts (TCs) from epidermoid cysts (ECs).

METHODS

Based on clinical and ultrasound features, a prediction model was established and validated. 164 cysts in the pilot cohort and another 69 in the validation cohort diagnosed with TCs or ECs histopathologically were evaluated. The same radiologist performed all ultrasound examinations.

RESULTS

For clinic features, TCs tended to occur in females compared with ECs (66.7 vs 28.5%; P < .001). In addition, TCs were prone to occur in the hairy area compared with ECs (77.8 vs 13.1%; P < .001). For ultrasound features, the internal hyperechogenicity and cystic change were more likely to appear in TCs in comparison with ECs (92.6 vs 25.5%; P < .001; 70.4 vs 23.4%; P < .001, respectively). Upon the features mentioned above, a prediction model was established with the areas under the receiver operating characteristic curves of 0.936 and 0.864 in the pilot and validation cohorts, respectively.

CONCLUSIONS

US is promising for differentiating TCs from ECs and is valuable for their clinical management.

Ultrasonographic Spectrum of Cutaneous Cysts With Stratified Squamous Epithelium in Pediatric Dermatology: Pictorial Essay

High-resolution ultrasound (HRUS) is an important diagnostic method in dermatology, especially in pediatric population. The most common type of cutaneous cysts in children corresponds to cysts with stratified squamous epithelium (CSSE). The objective is to present the different ultrasonographic appearance of histologically proven CSSE in a retrospective review. Epidermoid, milium, trichilemmal, dermoid, and pilonidal cyst and steatocystomas are included. Utility of HRUS in diagnosis of cutaneous lesions is well established. It is important to know-and stay updated-about the wide spectrum of ultrasonographic appearance of CSSE in order to avoid misleading diagnoses.

A rare ossifying trichilemmal cyst in a young female patient: Case report and literature review

Trichilemmal cysts constitute the second most common cutaneous cysts and are mostly presented on the scalp of middle aged women. It is, therefore, unusual for a young person to have a trichilemmal cyst and it is extremely rare for a trichilemmal cyst to be ossified. In literature, only 8 cases of trichilemmal cysts with concomitant ossification have been described. We report the case of a 22 year old female who presented with a scalp nodule and was treated via surgical excision of the lesion. The pathology examination of the surgical specimen revealed a lesion consisting of a multilayered squamous epithelium of slightly eosinophilic maturing keratinocytes. There was no granular layer, whereas the core of the lesion was occupied by mature bone tissue with calcium deposits. The definite diagnosis of the pathology report was ossifying trichilemmal cyst. The aim of this report is, to enlighten clinicians about this rare pathological entity.

Skin sonography in children: a review

Skin lesions are not uncommon in children, and most of them are benign. However, they can be a matter of concern. Although in most cases the diagnosis can be suspected based on clinical history and physical examination, in some cases clinical findings are nonspecific. High-frequency color Doppler US is a noninvasive technique that can play a relevant role in these cases and give important anatomical information for final clinical management. US can be helpful to avoid unnecessary surgery, plan a surgical excision and avoid advanced imaging studies such as MRI and CT, which have a lower resolution for the skin. Different lesions can look similar on US, and clinical correlation is always important. The purpose of this article is to show a variety of skin lesions that occur in children, emphasizing clinical-sonographic correlation, and to familiarize pediatric radiologists with the US technique and sonographic appearance of common skin lesions in children.