Lipomatosis of superficial peroneal nerve

Case contributed by Dr Maulik S Patel

Presentation

Right foot focal gigantism since birth. History of surgery in childhood. Complaining of right ankle anterior aspect elongated swelling with local pain for last 1 year.

Patient Data

Age: 20 years
Gender: Female

There is right foot enlargement with evidence of previous surgery. There is an elongated bulge along the anterior aspect of the ankle.

The clinically visible and palpable lesion is an elongated cord-like structure in the subcutaneous plane of ankle region. It extends proximally as well as distal to ankle joint. Length is about 70 mm. Its width is up to 15 mm and anteroposterior thickness up to 7 mm. The superficial peroneal nerve is within the lesion. This nerve is enlarged throughout its subcutaneous course in the distal leg - ankle - foot. The nerve is hyperechoic. It is surrounded all around by encapsulated fat. There is no vascularity in the lesion. This superficial nerve thickening with surrounding fat also extends (for about 10-15 mm) distal to nerve trifurcation.

There is a hypoechoic lesion (5 x 3 x 2 mm) at the distal end of nerve to 3rd toe (postoperative neuroma).

Other branches of the superficial peroneal nerve are not localized. Anterior tendons are intact. There is no anterior recess ankle joint effusion.

Intraoperative photo shows the fatty lesion at the site of clinically visible and palpable swelling. The second photo shows the excised lesion.

Case Discussion

A known case of focal gigantism presented with elongated swelling along the anterior aspect of the ankle. Ultrasound revealed fat between and around fascicles of superficial peroneal nerve. Histopathology of the lesion suggested lipomatosis of nerve.

Intraoperative and gross specimen photo courtesy of operating surgeon Dr. Mukesh Kapadia.

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