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Case 94

MRI of a female with leg mass

Schwannoma of the leg

Ozgur Kilickesmez

A 35-year-old female patient was referred with a soft tissue mass on the lateral side of the right leg, and local neuralgia. For further evaluation after ultrasonography (not shown here), MRI of the leg was performed.

Findings

There is a well demarcated, ovoid shaped, mass on the right side of the right fibula. The mass is hypointense on T1 WI, hyperintense on fat sat T2 WI and enhances strongly centrally.

Diagnosis

Schwannoma of the leg

Differential

Neurofibroma
Ganglion cyst
Malignant fibrous histiocytoma

Discussion

Schwannomas, also known as neurilemoma or neurinoma, are encapsulated benign slowly growing neoplasms arising from Schwann cells. They are asymptomatic until large enough to compress adjacent nerves, causing neuralgia. Lesions are almost always solitary, except in cases associated with neurofibromatosis. Schwannomas are surrounded by a true capsule of epineurium, and they displace nerve fibers and can be dissected and removed from the adjacent nerve without resultant neurologic damage. This is in contradistinction to neurofibromas, in which the adjacent nerve is infiltrated and cannot be dissected free. Schwannomas demonstrate a low to intermediate signal intensity on T1-weighted images and a heterogeneous hyperintense signal intensity on T2-weighted images on MRI. They show intense gadolinium enhancement. Atrophy may be seen along the long axis of the muscle adjacent to the lesion in approximately 25 % of the cases. Neurofibromas and ganglion cysts should be considered in the differential diagnosis of schwannomas. Neurofibromas have a more defined geographic internal architecture, characterized by low signal central region surrounded by a higher signal periphery on T2-weighted MR images. Ganglion cysts do not reveal gadolinium enhancement, and have much brighter content on T2-weighted MR images.

References

1. S.Cakirer, K. Kamberoglu, O. Kilickesmez, A. Kamberoglu. Schwannoma of the wrist.
2. Odom RD, Overbeek TD, Murdoch DP, Hosch JC. Neurilemoma of the medial plantar nerve: a case report and literature review. J Foot Ankle Surg. 2001 Mar-Apr;40(2):105-9. Review. PMID: 11324666
3. Torossian JM, Augey F, Salle M, Beziat JL. Giant foot schwannoma. Br J Plast Surg. 2001 Jan;54(1):74-6. PMID: 11121325
4. Kang HJ, Shin SJ, Kang ES. Schwannomas of the upper extremity. J Hand Surg [Br]. 2000 Dec;25(6):604-7. PMID: 11106529
5. Yamamoto T, Fujioka H, Mizuno K. Malignant schwannoma of the digital nerve in a child. A case report. Clin Orthop. 2000 Jul;(376):209-12. PMID: 10906877

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