A dumbbell-shaped orbital dermoid cyst with atypical bony communication adjacent to the zygomaticofrontal suture: a case report

Orbital dermoid cysts are congenital choristomas that typically occur near orbital suture lines. Although dumbbell-shaped orbital dermoid cysts have been previously described, they most commonly demonstrate communication through established orbital sutures with trans-sutural extension Variants exhibiting atypical bony communication without radiographic evidence of classical trans-sutural extension are uncommon and may present significant diagnostic and surgical challenges. We report an unusual presentation of a dumbbell-shaped orbital dermoid cyst with non-classical bony communication near the lateral orbital wall in a 20-year-old woman who presented with a 5–6 year history of left upper eyelid swelling, pain, and horizontal gaze restriction. She had been repeatedly misdiagnosed as having periorbital edema, allergic reactions, and insect bites. Magnetic resonance imaging (MRI) revealed a well-circumscribed intraorbital lesion measuring approximately 2.5 × 2 cm, with a small extraorbital component, mass effect on adjacent extraocular muscles, and an associated focal bony defect along the lateral orbital wall, without clear trans-sutural extension. Retrospective history revealed a childhood brow mass that regressed following minor trauma, raising the possibility of post-traumatic displacement of a superficial dermoid into deeper orbital planes. Surgical excision via a Lazy S incision demonstrated classic dermoid contents, including keratinous debris and hair, with a tunnel-like tract connecting the superficial and deep components. Histopathological examination confirmed a dermoid cyst lined by keratinized stratified squamous epithelium with adnexal structures and showed no evidence of malignancy. This case broadens the recognized spectrum of dumbbell-shaped orbital dermoid cysts by demonstrating atypical bony communication adjacent to the zygomaticofrontal region without radiographic evidence of classical trans-sutural extension. It also highlights the diagnostic challenges associated with delayed deep orbital presentation and underscores the importance of meticulous evaluation of communication tracts and bony defects during surgical excision to minimize recurrence risk.