Cellular proliferation characteristics do not account for the behaviour of horrifying basal cell carcinoma. A comparison of the growth fraction of horrifying and non horrifying tumours

This study compared the clinical features, histological subtype, growth fraction (by Ki67 immunohistochemistry)and proliferation pattern of 22 clinically defined horrifying basal cell carcinoma compared to 81 non horrifying lesions. Late presentation was associated with half of the horrifying tumours. The other half developed horrifying tumours despite early intervention. The horrifying tumours exhibited a variety of histological growth patterns. A total of 50% were infiltrative, 23% nodular and 18% micronodular. There was no difference in the growth fraction or proliferation pattern between horrifying and non horrifying tumours of similar growth pattern (P=ns), although infiltrative tumours in either group exhibited a significantly higher growth fraction than nodular tumours (P<0.01). This suggests that there is no intrinsic biological difference between horrifying and non horrifying tumours to account for their behaviour. We conclude that late presentation, failed or inadequate early management especially of infiltrative tumours (and other subtypes) determines the development of horrifying tumours.