Proliferating Trichilemmal Cyst Presenting as Limbal Mass Dr Pawan Prasher Sri Guru Ram Das Institute of Medical Sciences and Research, Amritsar, India Financial Disclosure: No financial interest

Introduction – Management of limbal mass can be challenging in terms of establishing clinical diagnosis, histopathology and treatment – Differential diagnoses for limbal mass include pinguecula, pterygium, papilloma, nodular episcleritis, phlycten, nevus, granuloma, dermoid, lymphoma, CIN, malignant melanoma, squamous cell carcinoma, ectopic lacrimal gland tissue, hemangioma, nodular fasciitis, amyloidosis and in association with dermatological disorders like xeroderma pigmentosum – Histopathology plays a key role in the management of suspicous lesions – Presented herein, is a case of proliferating trichilemmal cyst that presented as a limbal mass

Case Report A 25-year-old female presented with gradually increasing mass in the left eye for over one month. Associated with redness, mild irritation and watering. No history of trauma, surgery or any similar episode in the past. No history of any associated ocular or systemic illness

Ocular examination Visual acuity was 20/20 both eyes Slit lamp examination showed elevated nodular mass measuring 5 x 4 x 3mm at nasal limbus of left eye. The mass had gelatinous, pearly white appearance in the center with dilated vessels in the peripheral part. Associated epithelial irregularity of the adjacent cornea. The mass appeared to be mobile over the underlying tissues and was non-tender. The rest of ocular and systemic examination was unremarkable.

The patient underwent excisional biopsy of limbal mass Under local peribulbar anaesthesia, the mass was excised with 2mm surrounding healthy conjunctival tissue The mass was found not to be adherent to the underlying tissues The excision was followed by application of 0.04% mitomycin-C application on the scleral bed for 2 minutes Excised mass was sent for histopathology Post-operatively patient was put on topical moxifloxacin eye drops four times daily, prednisolone eye drops four times daily and ciprofloxacin eye ointment at bedtime

Histopathology Presence of islands of squamous cells with keratin filled cysts in the substantia propria.

Histopathology Cysts lined by stratified squamous epithelium The squamous cells showed abrupt keratinization, without any granular layer, consistent with trichilemmal keratinization There was no evidence of atypia.

There was formation of early pyogenic granuloma at 2 weeks post-op which resolved on increasing the frequency of topical prednisolone eye drops to every 2 hours. At one year post-op, patient showed well healed conjunctiva with no evidence of recurrence in the area of excision.

Discussion Trichilemmal cyst arises from outer root sheath epithelium of hair follicle Also known as wen, pilar cyst or isthmus-catagen cyst Most often found on the scalp, but has also been reported to occur in buccal mucosa Formation of proliferating trichilemmal cyst in the current case could be as a result of implantation of hair follicle cells from eyelashes while rubbing or migration from caruncle Management of trichilemmal cysts includes wide local excision with continued long-term surveillance

Discussion Being keratinous cysts, these cysts are similar to epidermal cysts Key differentiating feature: trichilemmal keratinization In this pattern, cells undergo an abrupt transition from the stratum spinosum to the keratinized layer without the formation of the granular layer Rarely, trichilemmal cysts can become malignant

Conclusions Proliferating trichilemmal cyst can present as a gradually progressing limbal mass It is a benign condition that needs to be distinguished from malignant squamous cell carcinoma which has similar presentation but different prognosis

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