Cancer can affect the foot in many different ways. Ay of the tissues in the foot can be a primary course for a tumor to develop, but also ay of the tissues in the foot could be a location for a metastasis from a more proximal cancer.
http://podiatryarena.com/index.php?tags/cancer/ (Podiatry Arena)
https://podiatryarena.com/index.php?threads/cancer-metastasis-in-the-foot.443/ (Podiatry Arena)
http://www.podiatryapps.com/the-oncologist/ (Podiatry Apps)