Zygomatic bone deformation caused by a periorbital epidermoid cyst in a child: a case report and literature review

Article information

Arch Craniofac Surg. 2026;27(3):146-150

Publication date (electronic) : 2026 June 20

doi : https://doi.org/10.7181/acfs.2025.0069

Jun Mo Kim, Woo Young Choi, Ji Seon Cheon, Jeong Yeol Yang

Department of Plastic and Reconstructive Surgery, Chosun University College of Medicine, Gwangju, Korea

Correspondence: Woo Young Choi Department of Plastic and Reconstructive Surgery, Chosun University College of Medicine, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Korea E-mail: woo3847@gmail.com

Received 2025 October 21; Revised 2025 December 19; Accepted 2026 June 20.

Abstract

INTRODUCTION

Epidermoid and dermoid cysts are benign congenital lesions that arise from ectodermal inclusions during embryologic development [1]. While dermoid cysts contain adnexal structures such as hair follicles or sebaceous glands, epidermoid cysts lack adnexal components and consist solely of stratified squamous epithelium with keratin debris [2,3]. Despite this histologic distinction, their clinical behavior, anatomic predilection, and imaging characteristics substantially overlap.

In the pediatric periorbital region, dermoid cysts represent the majority of cases, with reported incidence substantially higher than epidermoid cysts [1]. Both entities may be superficial or deep, and long-standing lesions can exert sufficient pressure on adjacent bone to produce smooth cortical erosion or remodeling [4]. Importantly, such remodeling does not necessarily indicate primary intraosseous origin. True intraosseous cysts of the zygoma remain exceedingly rare compared with calvarial or digital intraosseous epidermoid cysts [5,6]. Given the pliability of the pediatric craniofacial skeleton, the potential for spontaneous bone restoration after removal of the compressive source is high [7]. However, systematic documentation of such natural remodeling remains limited. This case report illustrates a pediatric periorbital epidermoid cyst with secondary zygomatic bone depression and summarizes relevant embryologic and clinical considerations.

CASE REPORT

A 26-month-old girl was referred to our department with a noticeable mass over the left eyebrow, first detected by her parents a month before consultation. She had no associated symptoms such as pain, redness, exophthalmos, or visual disturbances, and her medical history was unremarkable. Ultrasound examination revealed a well-defined, 9×9 mm mass at the left eyebrow. Computed tomography (CT) revealed a well-circumscribed cystic mass abutting the frontal process of the zygoma with smooth pressure-related indentation of the bony surface. Magnetic resonance imaging (MRI) identified a small lesion in the lateral aspect of the left orbit, adjacent to the frontal process of the left zygomatic bone. The lesion exhibited mixed high and low signal intensities on T1- and T2-weighted images with diffusion restriction. No significant soft tissue or vascular involvement was observed. The size was consistent with the ultrasound findings (Fig. 1).

Fig. 1.

A 26-month-old girl with a palpable mass over the left eyebrow. (A) Ultrasound showing a well-defined 9×9 mm cystic mass at the left eyebrow. (B) T1-weighted magnetic resonance imaging (MRI) demonstrating a small lesion with mixed high and low signal intensities adjacent to the frontal process of the left zygomatic bone. (C) T2-weighted MRI showing mixed signal intensities with diffusion restriction.

Based on the imaging features and location, the differential diagnosis included epidermoid cyst and dermoid cyst. Surgical excision was planned. Under general anesthesia, an incision was made above the left eyebrow to access the lesion. The lesion was carefully dissected from the surrounding tissues without disturbing the orbital structure. The periosteum was incised, and the fully encapsulated cyst was excised completely. The periosteum was then meticulously sutured, and the surgery was completed successfully.

Histopathologic examination confirmed an epidermoid cyst. The lesion showed a cystic structure lined by stratified squamous epithelium with a well-formed granular cell layer and abundant laminated keratin within the lumen (Fig. 2). Postoperative recovery was uneventful, with no orbital dysfunction or neurological symptoms. At 6 months of follow-up, there was no recurrence. The bone defect demonstrated substantial spontaneous regeneration, eliminating the need for synthetic materials or bone grafting (Fig. 3).

Fig. 2.

Histopathologic examination of the excised cystic lesion: Histological section demonstrating a cyst lined by stratified squamous epithelium with a prominent granular cell layer and abundant laminated keratin debris within the lumen. The cyst wall lacks adnexal structures such as hair follicles, sebaceous glands, or sweat glands, a key diagnostic feature distinguishing epidermoid cysts from dermoid cysts (hematoxylin and eosin, ×200).

Fig. 3.

Six-month postoperative outcomes. (A) Computed tomography (CT) scan taken immediately after cyst removal surgery. (B) CT scan demonstrating substantial natural bone recovery and defect healing 6 months after surgery.

LITERATURE REVIEW

Congenital dermoid and epidermoid cysts are among the most frequently encountered developmental inclusion lesions in the pediatric craniofacial region [1,3,8,9]. These lesions originate from sequestration of ectodermal tissue during embryologic development, most commonly along lines of fusion of craniofacial processes. Although dermoid and epidermoid cysts are histologically distinct, their clinical behavior, anatomic distribution, and treatment principles overlap substantially. For this reason, they are often discussed together when evaluating congenital craniofacial masses in children [1,8].

The embryologic origin of dermoid and epidermoid cysts has been attributed to abnormal inclusion of surface ectoderm during neural tube closure or earlier during gastrulation. Dermoid cysts contain both epidermal and dermal elements, including skin adnexal structures such as hair follicles, sebaceous glands, and sweat glands. In contrast, epidermoid cysts are composed exclusively of stratified squamous epithelium with a wellformed granular layer and laminated keratin, without adnexal components. While this distinction is definitive at the histopathologic level, it has limited impact on surgical management, as both lesions behave as benign, slow-growing masses that are effectively treated with complete excision.

From an epidemiologic perspective, the relative frequency of dermoid and epidermoid cysts varies by anatomic location. In the pediatric craniofacial region—particularly in the periorbital and lateral eyebrow areas—dermoid cysts are encountered more frequently than epidermoid cysts. In contrast, intracranial series demonstrate a different distribution, with dermoid cysts accounting for approximately 0.3% of all tumors, whereas epidermoid cysts comprise up to 0.5%–1.5%, indicating a relative predominance of epidermoid pathology in intracranial locations [3].

Accurate diagnosis of pediatric zygomatic and periorbital masses requires integration of clinical presentation, imaging characteristics, and histopathologic findings. CT is useful for evaluating cortical remodeling and bony involvement, whereas MRI provides superior soft-tissue characterization [10,11]. Diffusion restriction favors epidermoid cysts, while fat-containing components suggest dermoid cysts; however, imaging features may overlap, and definitive diagnosis relies on histopathologic examination.

The differential diagnosis of pediatric zygomatic and periorbital masses is broad and includes Langerhans cell histiocytosis, intraosseous hemangioma or vascular malformations, central giant cell granuloma, and benign fibrous histiocytoma (Table 1) [1]. Several of these entities may present with painless swelling and radiologic bone involvement, yet their biologic behavior, treatment strategies, and prognoses differ substantially. Lesions such as Langerhans cell histiocytosis or giant cell granuloma may demonstrate aggressive osteolytic changes and require systemic evaluation or adjunctive therapy, whereas dermoid and epidermoid cysts typically cause smooth pressure-related remodeling and are managed with complete surgical excision alone.

Table 1.

Differential diagnosis of pediatric zygomatic/periorbital masses

DISCUSSION

The present case illustrates a congenital periorbital epidermoid cyst located in a deep plane, producing secondary pressure-induced remodeling of the zygomatic surface rather than true intraosseous pathology. Recognition of this mechanism is clinically important, as smooth cortical depression caused by chronic external pressure may mimic primary osseous lesions and lead to unnecessary concern regarding aggressive disease.

Complete surgical excision with removal of the intact cyst wall remains the treatment of choice for both dermoid and epidermoid cysts. In pediatric patients, management of the associated bone contour change requires special consideration [7,8,12,13]. Recent evidence supports the potential for spontaneous osseous remodeling in pediatric patients. Yoo et al. [4] prospectively demonstrated predictable recovery of bone depression following craniofacial dermoid cyst excision in children, highlighting the remarkable remodeling potential of the pediatric craniofacial skeleton. Their findings align with the present case, in which substantial spontaneous bone regeneration occurred without grafting or the use of alloplastic materials. The intact periosteum likely played a central role in facilitating new bone formation. Pediatric periosteum is known for its robust osteogenic potential, and preservation of this layer may allow natural contour restoration even when a measurable defect remains following cyst excision. This supports a conservative approach in select patients with limited cortical involvement and well-defined lesions, in whom immediate reconstruction may be unnecessary.

The present case exemplifies a congenital periorbital epidermoid cyst occurring in a deep plane with secondary pressureinduced remodeling of the zygomatic surface rather than true intraosseous pathology. Its significance lies in reinforcing the embryologic and developmental principles governing these lesions, clarifying the distinction between primary osseous disease and secondary bone remodeling, and supporting a conservative, periosteum-preserving reconstructive strategy in young children. When viewed within the broader literature on congenital craniofacial dermoid and epidermoid cysts, this case contributes to a more precise understanding of their pathogenesis, epidemiology, diagnostic evaluation, and optimal management.

Article information Continued