Rhabdomyosarcoma of the foot

Case contributed by Dr Magdalena Chmiel-Nowak

Presentation

Slow-onset progressive swelling of the right forefoot.

Patient Data

Age: 17 years
Gender: Male
mri

There's an infiltrating soft tissue mass, spanning the length of the 1st to 3rd metatarsal bones, involving the muscles and tendons of the dorsum of the foot in this location as well as the interossei muscles in the 1st and 2nd web spaces. The lesion encases the 2nd metatarsal bone and is adjacent to the 1st and 3rd metatarsal bone, with no evidence of bony destruction. It is isointense on T1W1, hyperintense on T2WI, with slightly heterogeneous contrast enhancement. A small cystic area is visible superficially to the 2nd metatarsal shaft, which may correspond to an area of necrosis or a fluid collection.

Case Discussion

The patient originally presented to the ER with swelling and pain of the whole right lower limb. Ultrasound was negative for DVT but marked inguinal lymphadenopathy with femoral/external iliac vein compression was seen, as well as enlarged popliteal lymph nodes. A subsequent abdominal CT (not shown) showed marked periaortic and iliac lymphadenopathy. The patient admitted that some time ago he noted slow-onset progressive swelling of his right forefoot and MR examination of this area was performed (shown above).

A biopsy of the forefoot lesion and of one of the inguinal lymph nodes was performed, with intraoperative pathology reporting small blue round cells in both samples. Further histopathology reported alveolar rhabdomyosarcoma with lymph nodes metastasis.  

Rhabdomyosarcoma is the most common soft-tissue sarcoma in children, constituting more than half of the cases. The alveolar type accounts for approximately 20% of cases, is usually seen in adolescents and young adults and is often located in the extremities. It has the worse prognosis of all subtypes and lymph nodes involvement is an additional poor prognostic factor, which warrants an aggressive treatment approach.

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