A bump on the side of the foot could have various causes, including injuries, bursitis, and cysts. In some cases, causes can be serious and require prompt medical attention.

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A lump on the side of the foot is a common complaint. While some causes are of serious concern, many causes are not.

Still, it’s important to have any bump on your foot checked out by a doctor — even if it’s a small lump that’s not bothering you. Some foot bumps may be cancerous, so it’s critical that a medical professional accurately diagnose them.

If you’re wondering what the lump on the side of your foot could be, read on to learn some of the most common causes of foot bumps and book an appointment with a primary care physician or a foot specialist.

There are a variety of reasons why lumps could develop on the sides of your feet. Below are some of the most common causes:

  • Injuries. If you’ve recently injured the side of your foot, you may have a temporary lump along with swelling and bruising. Such lumps tend to resolve on their own as these symptoms decrease. However, pain or swelling that lasts more than 5 days should be addressed with a doctor.
  • Ganglion cysts. These benign, or non-cancerous, growths have a jelly-like texture and are most common on the tops of the feet, but they can occur on the sides, too. Ganglion cysts may not cause symptoms until they are large enough to rub against shoes, nerves, or joints, at which point you may feel pain or tingling sensations. Large ganglion cysts may be drained or surgically removed, but it’s still possible for them to grow back.
  • Bursitis. This painful condition develops when bursae, the small fluid-filled sacs in your feet, become inflamed. It’s typically caused by repetitive stress, such as certain physical exercises or wearing ill-fitting shoes. Bursitis can develop on the sides of your feet, as well as on your heels or big toes. The affected areas may be red and tender to the touch.
  • Plantar fibromas. Also benign, these masses tend to have a more solid texture than ganglion cysts. They aren’t typically painful, either. While plantar fibromas are most common on the bottoms of your feet, it’s possible for them to develop along the sides near the arch of your foot.
  • Lipomas. While not as common on the sides of the feet, these soft, fatty tissues are common with age in all areas of the body. These aren’t cancerous or particularly painful. Lipomas are generally left alone, but your doctor may surgically remove them if they bother you.
  • Diabetes. With diabetes, you may not be able to feel injuries in your feet, so it’s important to inspect them often. One possible type of foot lump seen in diabetes is a fungal infection called phaeohyphomycosis.
  • Accessory naviculars. Caused by extra cartilage or bone growth, these congenital bumps form on the inner side of your feet, and above your arches. Accessory naviculars can cause pain and redness, usually after wearing shoes and working out.
  • Malignant tumors. While less common, it is possible for some foot lumps to be malignant (cancerous).

While most of the common causes listed above aren’t considered life-threatening, it’s still important to get any unusual lump on the side of your foot checked out by a foot doctor.

It’s even more critical to see a podiatrist if any foot bumps are causing pain or discomfort — especially while walking.

You should also see a podiatrist if any foot pain is getting worse, or if the lump on your foot is rapidly growing larger.

You should also seek immediate medical treatment if any lumps are accompanied by symptoms of an infection, such as:

  • an open wound on your foot
  • any pus or discharge
  • fever
  • numbness or swelling that doesn’t improve within a few days
  • inability to put any weight on the affected foot

It’s estimated that only 4 to 5 percent of musculoskeletal tumors are located in the foot area, and most of these are benign. However, your doctor needs to rule out cancer to avoid serious complications.

To rule out a malignant tumor, your doctor will take a sample of the foot lump. If a lab test shows that the foot lump is cancerous, your doctor may order imaging tests to see the extent of the foot tumor before surgically removing it.

You may also be referred to an oncologist for further cancer treatment.

The following foot lump symptoms are considered red flags for potential cancer:

  • increase in pain
  • the lump continues to increase in size
  • larger size (more than 5 cm)
  • recurring lumps despite drainage or removal

Even if a lump on the side of your foot isn’t causing any pain or other symptoms, it’s important to have a doctor look at it. They can accurately diagnose the lump while also ruling out more serious issues such as an infection or cancer.

Unless your lump is associated with a minor injury, foot bumps don’t usually go away without treatment. Depending on the exact cause, treatment doesn’t always consist of surgery — for example, you may be able to have the lump drained.

See an orthopedic specialist or podiatrist to solve what’s causing the lump on the side of your foot. The sooner you get answers, the better the outcome.