Breast Cancer classifier using the K-Nearest Neighbors (KNN) algorithm

You probably know that October is the Breast Cancer Awareness Month and following my learning path I decided to write a simple-yet-powerful classifier that predicts whether a test result indicates a benign or malignant tumor using the K-Nearest Neighbors algorithm. I think the beauty of the KNN is its simplicity. In Brazil we have a popular saying that says: "tell me who you're with and I'll tell you who you are". The same happens in KNN: given a set of points in a n-dimensional space and a point X, we predict that the class of X will be the most predominant class among X's K-Nearest Neighbors. Let's use the poorly illustrated image bellow to exemplify.