Clinicohistopathologic Findings in Keratoacanthoma and its Immunohi-stochemical Study of Ki-67, p53, bcl-2 and Involucrin Protein Expression

Kwon, Sung Dae; Kye, Young Chul; Kim, Soo Nam

Abstract

BACKGROUND: Keratoacanthoma(KA) is common, benign cutaneous tumor that is most likely derived from hair follicle cells, and most often occurs on sun-exposed sites in light-skinned persons of middle age or older. Some authors believed that keratoacanthoma is a variant of squamous cell carcinoma(SCC), which it often resembles clinically and histopathologically. So, the distinction between KA and SCC is still debatable and a matter of speculation. OBJECTIVE: The purpose of this study was to investigate the clinicohistopathologic findings of KA and its expression patterns, compared with SCC, of immunohistochemical staining using Ki-67, p53, bcl-2, and involucrin. METHODS: This clinicohistopathologic study included 20 cases that had confirmed to KA. We performed the immunohistochemical staining with Ki-67, p53, bcl-2 in 14 and with involucrin in 13 KAs. Ki-67, p53, bcl-2, and involucrin staining was also performed in 6 SCCs. RESULTS: All of KAs were solitary lesions. The male to female ratio was 1.2:1. The average age was 63.315.1 years and 11 of 20(55.5%) developed in sixth and seventh decades. The site of predilection were sun-exposed areas(85%) such as face, forearm, neck. Histologically, all of KAs were fully-developed lesions, and 17 of 20(85%) were dome or berry-shaped type II KAs. 17 of 20(85%) KAs showed exo-endophytic growth pattern. Common histologic findings in this study were horn-filled crater formation(80%), epidermal collarette(85%), epidermal proliferation in the perilesional area and the base of crater(100%), lateral extension tendency(80%), individual keratinization(75%), intraepithelial neutrophilic microabscess(65%), and eosinophilic glassy appearance in kertinocytic cytoplasm(95%). In immunohistochemical study using Ki-67, p53, bcl-2, and involucrin, there were no significant differences between KA and SCC except of the distribution pattern of Ki-67 positive cells in tumor. Ten of 14(71.4%) KAs revealed the marginal pattern, whereas no SCCs showed marginal pattern in Ki-67 staining. CONCLUSION: KA is a rapidly growing, cutaneous tumor that most often occurs on sun-exposed sites in sixth and seventh decades. Our results showed that KA is almost similar to SCC immunohistochemically, we suggest that KA is a type of SCC. And also, the characteristic distribution pattern of Ki-67 positve cells is helpful in making differentiation between KAs and SCCs.