Shape detection in OpenCV

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I'm absolutely new to OpenCV and looking forward to great learning experiences in the same. Here I'm trying to detect blood cancer cells from the normal blood cells and thus giving an output in a yes/no. The image I'm using as a source is provided in the here http://www.indoamerican-news.com/wp-content/uploads/2013/02/Blood-cells.jpg. I'd be glad if someone could tell me the code as well as it's working. Thanks.