OSSN or Ocular Surface Squamous Neoplasia
Definition:
Ocular surface squamous neoplasia (OSSN) is a common malignancy of the squamous epithelium of the conjunctiva and cornea that comprises of the wide spectrum of dysplastic alterations. It can also be called as ‘skin cancer’ of the eye and ranges from “precancerous” lesions to bonafide invasive carcinoma.
Histological assessment of OSSN:
The histological assessment of OSSN depends upon the inhibition of neoplasia:
- Conjunctival intraepithelial neoplasia (CIN) or in situ is characterized by neoplastic cells contained by the basement membrane only. It can be graded as mild, moderate, or severe. The severe and advanced lesions are called squamous carcinoma in situ.
- Invasive squamous cell carcinoma is characterized by invasion of the neoplastic cells into the stroma.
Risk factors of OSSN
- Areas with high ultraviolet light B rays exposure
- Advanced age
- Male sex
- Ocular surface injury
- Ocular surgery
- Mutation of the p53 tumor suppressor gene
- Hereditary deficiency of DNA repair such as in xeroderma pigmentosum
- Immunosuppression in organ transplant recipients
- Heavy smoking
- Light pigmentation of the hair and eye
- HPV or HIV infection
Causes of OSSN
- Excessive sun exposure
- Exposure to various carcinogenic chemicals like petroleum products, trifluridine, arsenicals, beryllium
- Immune system suppressing drugs
- Old age
- Viral infection
- Vitamin A deficiency
Clinical presentation of OSSN
The clinical presentation of OSSN is wide and basically depends upon the extent of epithelial and stromal infiltration. It appears as a sessile, fleshy, and elevated lesion that have following characteristic presentation:
- Arises in the conjunctiva and extends towards the limbus to involve adjacent cornea
- Can also show isolated corneal involvement
- Most commonly occur at the 3 or 9 o’clock position
- Gelatinous appearance
- Round or oval in shape
- Nodular or diffuse lesion
- Pattern of blood vessels is irregular
- Slow growing
Symptoms of OSSN
- Mild discomfort in the eye
- Eye irritation
- None to severe eye pain
- Visual loss
Diagnosis of OSSN
Most of the cases of OSSN look like pterygium or unusual pterygium and is first noticed by patient and their friends. An examination of the eye using slit lamp can help the ophthalmologist but most of the cases gets confirmed only after surgical removal and histopathological examination of the excised or incised lesion or abnormal tissue by a pathologist. In addition to this, following less invasive modalities are also found to be helpful in evaluating the OSSN:
- Impression cytology
- Exfoliative cytology
- Fine-needle aspiration biopsy
- Confocal microscopy
- Ultra-high-resolution optical coherence tomography (UHROCT)
Treatment of OSSN
The various treatment modalities that are used to treat OSSN work best and show promising results when given in combination. These include:
- Topical and/or intralesional chemotherapy with interferon (IFN) alfa-2b, 5-fluorouracil (5-FU), or Mitomycin C (MMC)
- Immunotherapy
- Surgical complete excision of histopathologically proven tumour-free margins of OSSN
- Cryotherapy to the edges of excision
