OSSN.ppt

Editor's Notes

• #6: It has been speculated that OSSN may arise from dysfunctional limbal stem cells having been altered by various mutagenic agents, such as UV radiation.15 The mutagenic factors which have been best understood include exposure to ultraviolet B radiation, and infection with human papilloma virus. Other reported risk factors include exposure to petroleum products, heavy cigarette smoking, chemicals such as trifluridine, arsenicals, beryllium, ocular surface injury, vitamin A deficiency, light pigmentation of the hair and eye, defective DNA repair in Xeroderma Pigmentosum, family origin in the British Isles, Austria, or Switzerland, infection with HIV16,17 and other immunocompromised states.
• #7: Clinically OSSN has many presentations Leukoplakia indicate secondary hyperkeratosis, due to squamous cel dysfunction One often finds dilated conjunctival blood vessels feeding and draining the lesion. SCC is locally invasive and metastasis is seen in <2% of cases. It can invade intraocular tissues and orbit. Some lesions can be diffuse, flat, and poorly-demarcated without an obvious tumour making early diagnosis difficult. Massive tumours infiltrating the deeper corneal stroma and covering the entire ocular surface are also seen (Fig. 2A–F). Infiltrative variants of OSSN masquerading as necrotizing scleritis may pose a challenge in early diagnosis (Fig. 3 A–D).33 Rarely pigmented variants of OSSN may be seen making differentiation from conjunctival melanoma difficult (Fig. 1C).34
• #8:  (A). Slit lamp photograph under diffuse illumination shows papillary ocular surface tumour with prominent feeder (B). Figure shows a globular pink-coloured lesion arising with large feeder vessels. The lesion seems to be overlying a pterygium and was clinically mistaken to be a pyogenic granuloma (C). Figure shows a pigmented OSSN with feeder vessels (D). Slit lamp photograph under diffuse illumination showing large leukoplakic lesions with abnormal vessels
• #10: The gold standard for the diagnosis of OSSN is the histopathological evaluation of the lesion after an incisional or excisional biopsy However there are several occasions when the clinician may opt to do diagnostic tests to corroborate the clinical suspicion of OSSN. Diagnosis is based on the presence of the universal cytological criteria which included nuclear enlargement, hyperchromasia, irregular nuclear outline, coarse nuclear chromatin, and prominent nucleolcarcinom
• #11: This includes all smaller tumors (limbal tumors <4 clock hours or <15 mm basal dimension).[8] If the lesion is too large, an incisional biopsy (punch or incisional wedge) to first obtain a histopathologic diagnosis may be necessary before proceeding to more extensive treatment.[8]
• #12: Nasally wing shaped fibrovascular growth noted encroaching the cornea with stocker’s line seen Linear epithelial iron deposition (Stocker line)
• #14: When lower one third and lower two thirds of the epithelium shows abnormal transformation the lesion is termed as mild and moderate dysplasia respectively. When the abnormality involves more than 2/3rds of the epithelial thickness, however surface maturation is preserved, the lesion is termed as severe dysplasia. Involvement of full thickness of epithelium, however with retained integrity of epithelial basement membrane is termed as carcinoma in situ (Fig. 6A–D). As the lesion progresses from mild to severe dysplasia, the cells differentiate less and less, gradually losing their squamous features until eventually the full thickness of epithelium is made of undifferentiated/immature atypical cells which can even have basaloid like appearance
• #15: (A) Moderate dysplasia-squamous intra epithelial lesion, abnormal transformation of epithelium involving more than 2/3rds of epithelial thickness, however the degree of cytological atypia is not sufficient to term this lesion as severe dysplasia (B). Severe dysplasia-there is almost full thickness replacement by abnormal epithelium, surface maturation is noted with keratinisation. Basement membrane is intact. (C). Carcinoma- in-situ- there is full thickness replacement by abnormal epithelium with marked nuclear pleomorphism. Basement membrane is intact, (arrow marked) (Haematoxylin-eosin, X 400) (D). Invasive Squamous cell carcinoma-invasion of stroma is seen as tumour nests and broad expansive tumour masses
• #16: (A) Corneal OSSN-slit lamp photograph under diffuse illumination shows minimally elevated lesion involving ¾ of the cornea-scleral limbus. The corneal surface is covered by a greyish membrane with abnormal vessels (B). Atypical epithelium of the cornea, infiltration of corneal stroma is limited by intact bowmans membrane (arrow marked). An inflamed fibrovascular membrane is seen above the corneal stroma