Ocular surface squamous neoplasia (OSSN)
OSSN; conjunctival intraepithelial neoplasia (CIN); corneal-conjunctival intraepithelial neoplasia; conjunctival SCC; squamous cell carcinoma of the conjunctiva
Ocular surface squamous neoplasia is a spectrum of squamous proliferations of the conjunctiva and cornea — from mild dysplasia and carcinoma in situ (collectively CIN, conjunctival intraepithelial neoplasia) through to invasive squamous cell carcinoma. UV is the dominant risk factor; HIV and HPV are recognised co-factors, with substantially elevated incidence in sub-Saharan Africa. Clinically OSSN presents as a gelatinous, leukoplakic or papilliform plaque at the limbus or interpalpebral conjunctiva with feeder vessels. UK management combines topical chemotherapy (mitomycin C, interferon α-2b) with surgical excision using a no-touch technique and adjunctive cryotherapy. Specialist ocular oncology service involvement is essential for invasive disease.
Clinical features
- Gelatinous, leukoplakic or papilliform conjunctival mass at the limbus or interpalpebral conjunctiva — usually unilateral.
- Prominent feeder vessels and surface vascular hairpin loops.
- Corneal involvement appears as a translucent grey opacification with whorl-like patterns.
- Median age 60–70 in temperate climates; younger (~ 40–50) in equatorial regions and in HIV-positive individuals.
- Male predominance overall.
Risk factors
- Chronic UV exposure — the dominant risk factor; outdoor occupations, equatorial latitudes.
- HIV — substantial relative-risk elevation; OSSN is an AIDS-defining illness in some classifications.
- HPV — particularly HPV-16; co-factor; relevance debated.
- Xeroderma pigmentosum.
- Atopic / chronic ocular surface inflammation.
- Cigarette smoking.
Imaging and diagnosis
- Slit-lamp examination with rose-bengal or lissamine green staining — neoplastic epithelium retains stain.
- Anterior segment optical coherence tomography (AS-OCT) — highly characteristic abrupt transition from normal thin epithelium to thickened hyper-reflective neoplastic epithelium.
- Ultrasound biomicroscopy (UBM) — for deeper invasion / scleral involvement.
- Impression cytology or incisional biopsy for histological diagnosis (often after empirical topical therapy in obvious cases).
Management
- Topical chemotherapy first-line in most UK practice:
- Mitomycin C 0.02–0.04% drops, 4 × daily for 7 days, then 7-day rest, for 3–6 cycles.
- Interferon α-2b 1 million IU/mL drops, 4 × daily for 3–6 months.
- 5-fluorouracil 1% drops, 4 × daily for 4-day cycles, repeated.
- Topical therapy avoids surgical excision in many cases and is well-tolerated; the principal toxicity is conjunctival inflammation and toxic keratopathy.
- Surgical excision for tumours unresponsive to topical, large tumours, or those with invasive features:
- "No-touch" technique to avoid tumour seeding.
- 4 mm clear margins.
- Adjunctive double freeze-thaw cryotherapy to conjunctival edges.
- Amniotic membrane graft for large defects.
- Brachytherapy (Sr-90 or Ru-106) for residual disease, recurrent disease or scleral invasion.
- Orbital enucleation / exenteration — for advanced OSSN with deep scleral or orbital invasion.
- Concurrent assessment / treatment of HIV.
- Photoprotection — UV-blocking sunglasses, hat.
Prognosis
- Excellent prognosis for CIN / in situ disease — recurrence after appropriate treatment 5–10%.
- Invasive disease has higher recurrence; rarely regional or distant metastasis.
- Lifelong surveillance — 3-monthly for 1–2 years, then 6-monthly.
References
- Shields JA, Shields CL. Intraocular Tumors — Atlas and Textbook. Wolters Kluwer; 2016.
- Kim BH, Kim MK, Wee WR. Topical mitomycin C in ocular surface squamous neoplasia — meta-analysis. Cornea; 2016.
- Stuart KV et al. Ocular surface squamous neoplasia — incidence, management, prognosis. Br J Ophthalmol; 2020.
Spot a correction?
If any clinical statement, citation or link on this page needs updating, please email admin@skinoncology.net with the page name, the proposed correction and the supporting source.