Background: Basal cell carcinoma (BCC) is the most common malignancy in humans. Several factors have been associated with the biological behavior of these tumors, including histopathologic type, depth of tumor invasion, perineural invasion, and the expression of several biologic markers including Ki67, a proliferative marker. Previous studies assessing the relationship between the proliferative fraction, as expressed by Ki67, and the histologic variants of BCC as well as its association with the tendency to recur, failed to illustrate significant statistical correlation.

Objectives: To examine the proliferative index, as expressed by Ki67, in various subtypes of basal cell carcinoma, and to assess its relationship to various histological and clinical variables.

Methods: In this retrospective study 51 lesions of BCC were examined. In each case, the following data were gathered: demographic (age and gender), anatomic location, size of the lesion, and clinical follow-up.  Each case was stained immunohistochemically with anti-Ki67 antigen (MIB-1), and the proliferative index was determined. Histologic analysis was performed for the following data: presence of an ulcer, intensity of inflammatory infiltrate, histologic subtype, mitotic count, and the presence of perineural invasion.

Results: Basal cell carcinoma exhibited a wide variation of proliferative indices, ranging from 1% to 61%. A significant statistical correlation was observed between the proliferative index and the mitotic activity, tumor ulceration and brisk tumor-infiltrating lymphocytes.

Conclusions: The wide variation in the degree of proliferation (from almost no activity to highly proliferative tumors) suggests that basal cell carcinoma exhibits a wide spectrum of biological characteristics. Ulcerated lesions were characterized by high proliferative index. No true correlation was demonstrated between the proliferative index and the aggressive histologic subtypes, implying that other factors were more biologically significant. The degree of proliferation also showed significant statistical correlation with the degree of tumor infiltration by lymphocytes. The significance of this proliferation-associated increased immunogenicity needs to be further studied.