In subcutaneous MCTs, was the difference in MST between high mitotic count and low mitotic count groups statistically significant?

• A. No difference
• B. Yes, P = .05
• C. Yes, P < .0001
• D. Not reported

Answer: (C)

The key idea here is how tumor biology relates to outcome and how statistics tell us whether that relationship is real or due to chance. In subcutaneous mast cell tumors, a high mitotic count indicates more aggressive tumor behavior, which typically translates to shorter survival. When the analysis shows a P value of less than 0.0001 for the difference in median survival time between high and low mitotic count groups, that means the observed difference is extremely unlikely to be due to random variation. In other words, there is very strong statistical evidence that mitotic count affects survival in these tumors. A P value of 0.05 would be the usual cutoff for significance, but here the result is far more significant, reinforcing that the high versus low mitotic count groups truly differ in MST. Not reported would be incorrect since the finding was clearly stated as highly significant.