A study of stromal collagen in oral lichen planus, carcinoma in situ, early invasive squamous cell carcinoma, and normal mucosa using picrosirius red stain

Abstract

Background and Objectives: Oral lichen planus (OLP) is a chronic disease of uncertain cause commonly affecting oral cavity. Although the WHO has designated OLP as a “potentially malignant disorder,” controversies exist regarding its malignant potential. Collagen forms the principal component of stroma or extracellular matrix and its role in carcinogenesis is widely studied in other premalignancies. Although collagen at the basal complex of OLP is widely explored, studies on collagen in the connective tissue stroma are not reported to date. We aimed to observe the nature of collagen in connective tissue stroma of OLP using picrosirius red stain (PSR) under polarized microscope and compare with buccal mucosa without any pathology related to exposure to tobacco and other oral carcinogens, carcinoma in situ (Ca in situ), and early invasive squamous cell carcinoma (EISCC). Materials and Methods: Eighty samples were observed, with twenty samples in each study group. Two 4–6-μ thick sections were obtained from the archival blocks. One section was stained with hematoxylin and eosin for confirming the diagnosis, whereas PSR staining was done for the other section. Both sections were analyzed using a polarizing microscope for evaluating the polarization colors of collagen. The images captured were stored on a computer. Five nonoverlapping fields were selected from each section in all groups and the thickness of five collagen fibers from each section was measured in microns using image analysis software and the polarizing color was also noted. The values obtained were compared using Kruskal–Wallis H-test and Chi-square test. We also used Mann–Whitney U-test for intergroup comparison. Results: The mean width of thick as well as thin fibers was more in controls than Ca in situ, OLP, and EISCC in decreasing order. Mature fibers were predominant in the controls than Ca in situ, OLP, and EISCC in decreasing order. Immature fibers were predominant in EISCC, followed by OLP, Ca in situ, and controls. Comparison of collagen in OLP and Ca in situ showed no statistically significant result in terms of thickness and polarization colors confirming a similarity in the nature of collagen in these two lesions. Conclusion: The stromal collagen of OLP was comparable to Ca in situ suggesting a change in the structure and organization of collagen probably attributed to the role of inflammatory mediators. A study with bigger sample size is recommended to evaluate the role of collagen in malignant transformation of OLP.