Pterygium—The Good, the Bad, and the Ugly

Abstract

Pterygium is a multifaceted pathology that displays apparent conflicting characteristics: benign (e.g., self-limiting and superficial), bad (e.g., proliferative and potentially recurrent) and ugly (e.g., signs of preneoplastic transformation). The natural successive question is: why are we lacking reports showing that pterygium lesions become life-threatening through metastasis, especially since pterygium has considerable similarities with UV-related malignancies on the molecular level? In this review, we consider how our pathophysiological understanding of the benign pterygium pathology overlaps with ocular surface squamous neoplasia and skin cancer. The three UV-related disorders share the same initial insult (i.e., UV radiation) and responsive repair mechanisms to the ensuing (in)direct DNA damage. Their downstream apoptotic regulators and other cellular adaptations are remarkably alike. However, a complicating factor in understanding the fine line between the self-limiting nature of pterygium and the malignant transformation in other UV-related diseases is the prominent ambiguity in the pathological evaluation of pterygium biopsies. Features of preneoplastic transformation (i.e., dysplasia) are used to define normal cellular reactions (i.e., atypia and metaplasia) and vice versa. A uniform grading system could help in unraveling the true nature of this ancient disease and potentially help in identifying the earliest intervention point possible regarding the cellular switch that drives a cell’s fate towards cancer.

Transcriptome Analysis of Pterygium and Pinguecula Reveals Evidence of Genomic Instability Associated with Chronic Inflammation

“…Genomic instability is caused by defects in certain processes that control the way cells divide, and involves genes encoding DNA damage repair proteins and genes encoding proteins involved in DNA and chromosome replication. This aptly describes our first group of DEGs, and their differential expression is consistent with the variable pathological characteristics of epithelia atypia and dysplasia ([ 43 ] and Supplementary Table S1 ).…”

“…In these comparisons, different cancer types within the general category were identified as activated or inhibited by their z-score. This finding emphasizes the often-noted similarities between pterygium and cancer [ 43 ].…”

UV Protection in the Cornea: Failure and Rescue

“…Autophagy modulating treatments such as resveratrol eye drops are already being researched to address several eye diseases [ 157 , 158 , 159 , 160 ], but their exact effect on corneal autophagy in not known. It had already been acknowledged that autophagy likely plays an important role in some UV-induced and UV-propagated diseases such as dry-eye disease and pterygium [ 161 , 162 ]. It has also been theorized that the activation of autophagy and autophagic flux, several pathological conditions in the corneal epithelia and stroma may be prevented [ 163 ].…”

Expression profiling suggests the involvement of hormone-related, metabolic, and Wnt signaling pathways in pterygium progression

“…Pterygium is a benign ocular surface disease that typically appears as a fibrovascular conjunctiva thickening from the nasal side and may progressively extend onto the cornea, causing visual impairment ( 1 , 2 ). The incidence of pterygium was 1.4% in the Asian population and 2.1% in the Chinese ( 3 ).…”