OSSN

1. 786/92
Compiled by: Dr. Iddi Ndyabawe
OCUlAR SURFACE SQUAMOUS NEOPlASIA [OSSN]
~ BASICS
DESCRIPTION
• The term •ocular surface squamous neoplasia (OSSN)• describes a spectrum of conjunctival
and corneal epithelial dysplasia ranging from conjunctival/corneal intraepithelial dysplasia (CIN)
to squamous cell carcinoma (SCC).
- CIN is analogous to actinic keratosis and does not invade conjunctival substantia propria or
corneal Bowman's layer.
o Mild CIN: partial dysplasia of epithelium.
o Severe CIN (carcinoma in situ): full-thickness intraepithelial neoplasia.
- Invasive SCC (when neoplasia breaches the basement membrane) is locally invasive and may
metastasize in 1-2%.
EPIDEMIOLOGY
lncidence
• Most common tumor of the ocular surface
- 0.03/100,000 persons in the U.S. (only of SCC; 18-year period)
- 0.13/1 00,000 persons in Uganda (6-year period)
- 1.9/100,000 persons in Australia (10-year period)
Prevalence
• Ranks among the top three most common ocular surface malignancies with melanoma and
lymphoma
• In one pathology series, it was the most prevalent malignancy of the ocular surface at 4% of
2,455 conjunctival lesions in adults.
RISK FACTORS
• Advanced age (>60 years)
• Male
• Smokers
• Light complexion
• Exposure to UV light or petroleum products.
• Human papillomavirus (H PV) 16 and 18 (conflicting data)
• Atopic eczema

2. Genetics
Expression of aberrant p53 tumor suppressor gene observed in 73% of ocular surface sec.
GENERAL PREVENTION
• Smoking cessation
• Protection from the sun
PATHOPHYSIOLOGY
UV-induced mutation or HPV-encoded destruction of p53 gene
ETIOLOGY
UV light. HPV infection
COMMONLY ASSOCIATED CONDITIONS
• HIV/AIDS
• lmmunosuppressed state
• Xeroderma pigmentosum
• Atopic eczema
• Organ transplantation
~ DIAGNOSIS
HISTORY
• Presenting symptoms: ocular irritation
• Ask. about history of smoking, sun burns. And chemical exposure.
• Ask about prior eye medications and surgery.
• Ask. about systemic conditions.
PHYSICAL EXAM
• Commonly occur in the exposed interpalpebral area at or near the limbus
- Conjunctival component can be gelatinous papilliform, or leukoplakic (white due to
hyperkeratosis).
- Corneal component appears as a translucent. Gray epithelial sheet with pseudopodia-like
margins.
- Rose bengal staining helps to delineate tumor margins.
• Invasive SCC can be fixed to the underlying tissue and have large feeder vessels, with varying
amounts of leukoplakia.
• CIN and SCC cannot be differentiated based on clinical features alone.

3. • Gonioscopy to evaluate iris and trabecular meshwork
• May be pigmented in patients with dark complexion
DIAGNOSTIC TESTS & INTERPRETATION
Lab
Initial lab tests
HIV test if OSSN present in a young adult.
Follow-up and special considerations
• Gonioscopy to evaluate for invasion of iris and trabecular meshwork through which sec can
access the systemic circulation.
• Uveitis and high intraocular pressure in the setting of known sec should be considered to have
intraocular invasion until proven otherwise.
Imaging
Initial approach
Ultrasound biomicroscopy to estimate the depth of limbal invasion of the sec.
Follow-up and special considerations
• Two less common but more aggressive variations of sec are the following:
- Mucoepidermoid carcinoma: affect the elderly, has yellow mucinous cysts, tendency for
intraocular and orbital invasion
- Spindle cell carcinoma: greater tendency to metastasize
Diagnostic Procedures/Other
• Primary complete excisional biopsy is most appropriate if possible.
• Map biopsy for large and diffuse OSSN in which a plan for topical chemotherapy is considered.
• Some advocate impression cytology to establish the diagnosis.
• Rose bengal staining helps delineate tumor margins.
Pathological Findings
• Mild ClN: partial-thickness replacement of the epithelium by anaplastic cells that lack normal
maturation

4. • Severe CIN: full-thickness replacement of the epithelium by anaplastic cells
• Invasive SCC: anaplastic squamous cells displaying hyperkeratosis and dyskeratosis invading
the underlying stroma and adjacent tissues.
- Mucoepidermoid carcinoma: a malignant epithelial lesion containing both mucinous and
epidermoid differentiation, which immunostain for acid mucopolysaccharide and cytokeratin
markers, respectively.
- Spindle cell carcinoma: also k.nown as sarcomatous carcinoma with both epithelial and
mesenchymal differentiation, which immunostain for cytokeratin markers and vimentin,
respectively.
DIFFERENTIAL DIAGNOSIS
• Benign
- Conjunctivitis (for diffuse, flat OSSN)
- Pinguecula, pterygium
-Papilloma
- Pyogenic granuloma
-Nevus
• Malignant
- Amelanotic melanoma
- Sebaceous carcinoma
- Metastasis
TREATMENT
MEDICATION
Not relevant (complete excision preferred)
ADDITIONAL TREATMENT
General Measures
Complete surgical removal with negative margins is most desirable for tumor removal and
diagnostic
confirmation.
Issues for Referral
Because of high recurrence after an incomplete removal, early referral to an Ocular Oncology
Service may be considered.