Key Identifiers in Cancerous Conjunctival Lesions

Ocular surface squamous neoplasia (OSSN) and pterygia are misdiagnosed in everyday practice about 60% of the time.¹ Because one of these is cancerous, a misdiagnosis rate that high is unacceptable. This article discusses key factors to consider when differentiating between these two conjunctival lesions (Figure).

SPOT THE DIFFERENCES

Pterygia, which are not cancerous, are caused by conjunctival degeneration, which forces the tissue to proliferate. They tend to occur in areas with high sun exposure (eg, equatorial regions) and in older populations.² Other risk factors include HIV, human papillomavirus infection, and smoking. Pterygia tend to have a wing-shaped appearance and are found at the 3:00 and 9:00 clock positions, almost always bilaterally. The vascularity follows the trajectory of the lesion and apex toward the cornea.

OSSN originates from basal epithelial cells and can invade the basement membrane over time. Although usually similar in appearance to pterygium, these lesions can be more elevated and vascularized. They can be located at any area of the interpalpebral limbal zone, although they are most often nasal and will typically be unilateral, have a feeder vessel, and involve the limbal region.

In your evaluation, ask patients to compare old pictures of themselves in which the lesion is visible (ie, from a year ago) with more recent photos. Change in the size or appearance of the lesion may indicate a malignancy.

DIAGNOSIS AND TREATMENT

Get into the routine of using rose bengal dye or lissamine green staining with any suspicious conjunctival lesion you encounter; OSSN will show positive staining. Anterior segment OCT should also be performed to view the cross-sectional appearance of the lesion. OSSN appears hyperreflective and shows an abrupt transition from normal to abnormal tissue.

Historically, OSSN has been treated with biopsy and surgical excision, but now, topical chemotherapeutics have become front-line therapy. Mitomycin may be dosed four times daily in 1 week on, 1 week off cycles, or 5-fluorouracil can be prescribed 1 month on, 1 month off.

EMPHASIZE THE NEED FOR SUN PROTECTION

If the lesion is truly a pterygium, encourage the patient to use sun protection and extensive lubrication with artificial tears to help with ocular irritation. If the pterygium is inflamed, a mild topical steroid can reduce symptoms. Surgical removal may be indicated if the pterygium invades the patient’s line of sight, but take care to advise the patient that it can reoccur. Any atypical pterygium should be referred out, as it may require a biopsy and further testing.