MKI67 and nodular malignant melanoma: In nodular melanomas, tumor necrosis (sparse or significant) was observed in 57 (29%) of the cases and was associated with increased tumor thickness (median thickness 5.2 mm when necrosis was present, as compared to 3.0 mm in cases without necrosis; p < 0.0001), and with increased tumor cell proliferation by Ki-67 (35% versus 25% positive nuclei; p = 0.007).