Use of proliferation rate, p53 staining and perforating elastic fibers in distinguishing keratoacanthoma from hypertrophic lichen planus: a pilot study

Background: Distinguishing keratoacanthoma (KA) and hypertrophic lichen planus (LP) histopathologically can be difficult, and the challenge is compounded by the tendency of KA to arise in association with hypertrophic LP. Methods: In this pilot study, we compared 18 cases each of KA and hypertrophic LP for proliferation index (MIB‐1), p53 staining and the presence of perforating elastic fibers (elastic Verhoeff‐van Gieson) to determine the utility of these staining modalities in distinguishing KA from hypertrophic LP. Results: Proliferation index in KA compared to hypertrophic LP is 88.2 (mean positive MIB‐1 cells/×100 field), SD = 56.6 and 47.3, SD = 68.4, respectively. p53 staining in KA compared to hypertrophic LP is 251 (mean positive cells/×100 field), SD = 117 and 158, SD = 119, respectively. Fifteen of eighteen (83%) keratoacanthomata demonstrate perforating elastic fibers compared to 1/18 (6%) for hypertrophic LP. Conclusion: Proliferation index is not significantly different between KA and hypertrophic LP (p = 0.059). Expression of p53 is increased in KA over hypertrophic LP (p = 0.024). The presence of perforating elastic fibers in KA is significantly different from hypertrophic LP (p < 0.0001) and suggests that elastic Verhoeff‐van Gieson staining may be of practical benefit in distinguishing KA from hypertrophic LP in difficult cases. Bowen AR, Burt L, Boucher K, Tristani‐Firouzi P, Florell SR. Use of proliferation rate, p53 staining and perforating elastic fibers in the distinction of keratoacanthoma and hypertrophic lichen planus: a pilot study.