Ocular Surface Squamous Neoplasia (OSSN): Diagnosis and Topical Chemotherapy
Last updated: November 2026
Ocular surface squamous neoplasia (OSSN) covers the spectrum from conjunctival intraepithelial neoplasia to invasive squamous cell carcinoma. It often looks like a pterygium or a patch of leukoplakia, so every atypical limbal lesion needs a second look.
Risk factors
- Ultraviolet exposure, older age, fair skin.
- HIV infection (a young patient with OSSN should be tested), HPV, immunosuppression, smoking.
Clinical features
- A gelatinous, leukoplakic or papilliform limbal lesion, usually in the interpalpebral zone, with feeder vessels.
- Corneal extension with a grey frosted edge.
- Signs of invasion: fixity to the sclera, large size, intraocular or orbital spread.
Diagnosis
- High-resolution anterior segment OCT: thickened hyperreflective epithelium with an abrupt transition (useful to diagnose and to monitor treatment).
- Impression cytology or biopsy; histology after excision.
Treatment
| Option | Details |
|---|---|
| Surgery | Wide "no-touch" excision with 3–4 mm margins, alcohol epitheliectomy for corneal parts, double freeze-thaw cryotherapy to the conjunctival margins |
| Topical 5-fluorouracil 1% | Cycles of 1 week on, 3 weeks off; cheap and well tolerated: popular in India |
| Topical mitomycin C (0.02–0.04%) | Cycles of 1 week; more toxic (pain, limbal stem cell deficiency); punctal plugs reduce side effects |
| Topical interferon alfa-2b | Best tolerated, slower, costly |
| Advanced disease | Enucleation or exenteration, radiotherapy, oncology input |
Topical chemotherapy can be used alone for non-invasive disease, before surgery to shrink a lesion, or after surgery for positive margins. Recurrence is common: follow up for years.
Where residents slip
- Calling a gelatinous limbal lesion a pterygium and doing bare sclera excision.
- Forgetting HIV testing in young patients.
- Touching the tumour during excision (seeding).
Test yourself: flip cards
Related: Pterygium for Residents: Grading, Surgery and Preventing Recurrence, Ocular Tumours: Eyelid, Conjunctiva, Uvea and Orbit, Eyelid Tumours.
Key sources
- Shields CL, Shields JA. Tumors of the conjunctiva and cornea. Indian J Ophthalmol. 2019;67:1930-1948
- Hollhumer R, et al. Ocular surface squamous neoplasia: management and outcomes. Eye. 2021;35:1562-1573
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