Presentation
Bulge/swelling in 1st web space of left foot during walking for about 1 year. Mild local pain. No trauma.
Patient Data
There is a well-defined dumbbell shaped lesion in the 1st web space. It is separate from bones/ joints/ tendons. At rest, the lesion is more visible from dorsal view than planter view. With compression of toes, lesion pops up on dorsal aspect. With compression of the lesion on dorsal aspect, lesion pops up on plantar aspect. It measures about 21 x 20 x 12 mm. Lesion is solid, homogeneously hypoechoic without calcification/ cystic changes. Posterior acoustic enhancement present. There is intralesional flow.
Continuity of lesion with nerve was not looked for at the time of the scan.
Microscopic sections show features of schwannoma (neurilemmoma) showing clusters of cells having wavy pointed nucleus and pink cytoplasm with indistinct cell borders, forming Antoni-A areas and Verocay bodies. Less cellular areas show prominent hyalinized vessels and fibrous tissue.
Courtesy of Dr Bharat Tandel MD (Pathology)
Case Discussion
An elderly female presented with swelling in 1st web space of foot. Based on the ultrasound showing a dumbbell-shaped, hypoechoic lesion with vascularity, the possibility of the lesion being a Morton's neuroma was suggested. The histopathology revealed findings more consistent with schwannoma.