“Cancer” is not just one disease, but is really a category of literally 100’s of different diseases, so the manifestation of a cancer is the foot is going to be very different depending on the type of cancer, just like it is in any other part of the body.
Cancer can manifest in the foot in many ways, for example:
There are a multiple variety of types of skin lesions that on rare a occasion may be due to a skin cancer (eg squamous cell carcinoma).
There may be a wound or sore that just does not heal with the usual treatments. On rare occasions that may be a skin cancer.
Toe Nail changes:
Changes in the appearance and growth of the toe nails may be indicative of an underlying disorder that needs to be investigated carefully.
Lumps and bumps:
Cancer may affect the bone and soft tissues and that may results in the deep palpable lump on the foot. There are many other much more common causes of these lumps and bumps than a cancer, but if there is anything unusual about the lump, it does need to be checked out for something more serious.
Foot pain is caused by a lot of different things. A cancer is the least likely and probably rarest cause, but health professionals need to have an “index of suspicion” when the clinical features associated with the pain do not quite match a known conditions and investigate further. The cancer may be primary and start in the foot or it may be secondary and be a metastasis to the foot from a cancer elsewhere (and that cancer may or may not have been diagnosed yet and on extremely rare occasions the metastasis and pain in the foot is the first sign of the cancer elsewhere).
Cancer in the foot is rare, but does happen. Anyone involved in treating the foot must have the skills to recognize the suspicious signs as the consequences of not detecting the cancer early has ramifications.