Frequent loss of p16 protein expression and high proliferative activity (Ki-67) in malignant melanoma from black Africans.

Malignant melanomas in black Africans are predominantly located on the lower extremities. Since their biological features have not been well focused, we studied 28 such cases with special reference to proliferative activity (Ki-67 expression), p16 and p53 staining, as well as microvessel density, all known to be involved in the progression of melanomas among whites. The findings were related to clinico-pathological characteristics. The tumours had a median thickness of 6.4 mm, ulceration was present in 71%, and vascular invasion in 36%, indicating the presence of advanced and aggressive melanomas. Further, loss of p16 protein expression was found in 50%, and high proliferative activity was present (median 41%). In contrast, strong p53 staining was rare (11%), although most tumours showed low-level positivity. Angiogenesis, as estimated by microvessel density, was significantly associated with vascular invasion (p = 0.022), supporting its role in the progression of these tumours. Thus, our findings indicate that melanomas located on the lower extremities in black Africans show several features of aggressiveness; in particular, the proliferative activity was high, and p16 alterations was frequent as evidenced by loss of protein staining. Our findings also indicated that the diagnosis is delayed among black Africans.