Abstract
Purpose :
Several reports have documented pre-cancerous lesions within pterygia. Although conjunctival melanosis is a common occurrence, evaluations of their character within pterygia are few. We sort to investigate immunohistochemistry staining patterns of these lesions and gauge their potential to proliferate.
Methods :
Pterygium specimens collected at one hospital center, between January 2000 to December 2015, noted to have melanosis within the body of the pterygium were stained with microphthalmia transcription factor (MITF), a nuclear protein expressed in benign and malignant melanocytes, Melan-A (MART1), a marker of melanocytic differentiation and Ki67, a marker of cell proliferation. All specimens were analyzed by one pathologist.
Results :
Nine out of 604 pterygium specimens, from 8 patients, were observed to have melanotic lesions within the pterygia on hematoxylin and eosin (H&E) stains. Two patients were Black, five, Hispanic and one, Indian. All were primary pterygium excisions. Expression of MITF and Melan-A was diffuse in all cases of pterygia with conjunctival nevi (intraepithelial and blue nevi). In all cases, MITF and Melan A showed increased melanocytic density at the stromal-epithelial junction consistent with staining patterns in primary acquired melanosis (PAM). Focal intraepithelial expression was also noted for both markers. Expression of Ki67 was low and less than 5% in both nevi and areas of melanosis. No atypia or malignant lesions were identified.
Conclusions :
These markers are useful in the evaluation of melanocytic lesions in pterygia and showed staining patterns consistent with PAM. The diffuse expression of MITF and Melan-A, including areas not observed to be pigmented in H&E stained sections, indicates that melanosis is diffuse. Because these lesions have the potential to proliferate and transform into malignant lesions, patients with pigmented pterygia should be followed closely.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.