Case Presentation

The patient is a 16 year old healthy male. For approximately 2 years, he has had a bump in the arch area of the right foot, which has been growing gradually. It has been bothering him slightly for about the last year, but it was never painful. Rather, there was difficulty walking normally due to the presence of the bump. The patient has no history of injury to the area. Initially, he saw a chiropractor and had treatment with no relief. Recently he was seen and referred by his orthopedic surgeon and podiatrist.

On examination, there is a slight limp. Upper lower extremity examination reveals no unusual skin lesions. Circulatory status of the extremity is unremarkable except were noted.

There is no local or regional lymphadenopathy, and no lymphadenopathy is noted in the draining lymph chain. No central lymphadenopathy is noted. There is no café au lait spot, or other unusual skin lesion. The patient appears otherwise health and well nourished.

Examination the foot shows an abnormal position, there is eversion of the foot and clawing of the second third and fourth toes. The toes are also slightly discolored and bluish. There is a visible and palpable mass in the plantar aspect of the foot that begins in the midportion of the arch and extends into the area of the metatarsal heads, which is deep, firm, and nontender. There is no pulsation, warmth, erythema, or tenderness.

Clinical images:

C1 C2

Plain radiographs are available for review and show an abnormality between the third and fourth metatarsal base, as well as clawing of the central three toes.

Plain radiographs:

X1 X2 X3 X4

An MRI shows a large mass that cannot be characterized based on the images, which is in the plantar aspect the foot, and it does surround some of the mid portions of the metatarsals. The mass abuts the first and second metatarsals, and the marrow signal in the second and third metatarsal may be abnormal.

MRI images:

M1 M2 M3 M4

The mass also seemed to surround the flexor tendons and the neurovascular bundles in the plantar aspect of the middle 3 metatarsals.

Biopsy is pending. What is the differential? What is the most common soft tissue sarcoma in the foot? What is the most common malignancy of any type in the foot? If a soft tissue mass is painless, is that a generally a good sign?

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