Explanation of Answers:
Q.1 Conjunctival intraepithelial neoplasia (CIN) and squamous cell carcinoma (SCC) are a spectrum of disease. CIN becomes SCC when malignant squamous cells invade the epithelial basement membrane. Thus, they have similar risk factors. Risk factors include being an older male, having a fair complexion, increased ultraviolet (UV) light exposure, Human Papillomavirus (especially HPV 16 and 18) and living at LOWER latitudes. Other potential risk factors include smoking, exposure to petroleum products and chemicals such as trifluridine and beryllium, ocular surface injury and HSV-1. SCC is more aggressive in those that are HIV positive and those with xeroderma pigmentosum.
Q.2 The limbus in the interpalpebral area is the most common location for both CIN and SCC.
Q.3 Appropriate therapy for SCC includes wide surgical excision with cryotherapy to the adjacent conjunctiva and application of absolute alcohol to the adjacent corneal epithelium and the underlying sclera. Depending on the depth of invasion of the malignant cells, partial- or full-thickness sclerectomy and scleral graft may be required. Chemotherapy (i.e. MMC, 5-FU and interferon) can be a useful adjuvant to the surgical treatment, but is most effective for more superficial disease. Radiotherapy can also be a useful adjuvant to surgery, but is not an effective treatment alone. When there is Intraocular or intraorbital invasion, enucleation or exenteration may be appropriate.