PMC5830161_01
A 59-year-old woman presented with a 1-month history of numbness on the plantar surface of her left foot. Discomfort occasionally radiated proximally along the medial aspect of the calf. She had a traumatic history of hitting the bottom of her foot on a sharp rock. On physical examination, obvious wasting of the left abductor halluces and foot intrinsic muscles was seen (arrow).
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On physical examination, obvious wasting of the abductor halluces and foot intrinsic muscles on the left foot was visible ( Fig. 1 ).
Plexiform neurofibroma. Multiple hypoechoic round masses surrounded by a hyperechoic background. The diameter of each mass measured 0.5 to 0.8 cm. (
A
) Short-axis ultrasound (US) image obtained over the calcaneus shows plexiform neurofibroma as a fusiform solid hypoechoic mass (arrow). (
B
) Long-axis US image obtained over the calcaneus shows plexiform neurofibroma as a cordlike hypoechoic mass (arrow). (
C
) T1-weighted image shows a multiloculated tubular lesion within the tarsal tunnel (arrow). (
D
) T1-weighted image shows a cordlike mass lesion below the calcaneus (arrow). (
E
,
F
) T2-weighted image shows a multiloculated tubulocystic lesion along the tibial nerve, lateral plantar nerve, proximal medial plantar nerve, and posterior calcaneal nerve, from the distal tibial plafond level to the fifth metatarsal base level.
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We also identified fusiform swelling of the nerve, which was indicative of tumor origin from a neurofibroma ( Fig. 2A , B ). Fig. 2C , D ) and high-signal intensity on T2-weighted images ( Fig. 2E , F ). Findings on physical examination and imaging were consistent with a diagnosis of a PNF of the foot. 
A multiloculated plexiform mass originated from the posterior tibial nerve (
A
). Plexiform arrangement (x10, hematoxylin and eosin [H&E] stain) (
B
) composed of wavy spindle cells (x400, H&E stain) (
C
) on histopathological examination.
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The mass originated from the posterior tibial nerve and involved the calcaneal branch, medial plantar nerve, and lateral plantar nerve ( Fig. 3A ).  Histopathological examination of the excised mass confirmed the diagnosis of PNF ( Fig. 3B , C ).