Keywords:
Extremities, Musculoskeletal soft tissue, Neuroradiology peripheral nerve, MR, Conventional radiography, Surgery, Education, Decision analysis, Education and training
Authors:
E. Gezmis1, S. K. Muratli1, F. Ulu Öztürk2, C. Altın1; 1Izmir/TR, 2Ankara/TR
DOI:
10.1594/essr2016/P-0006
Background
Introduction: Neurofibromas are benign peripheral nerve sheath tumors composed of Schwann cells,
fibroblasts and collagen.
Unlike schwannomas they are not encapsulated and infiltrate between the nerve fascicles causing fusiform enlargement of the nerve.
They account for slightly more than %5 of all benign soft tissue tumors (1,2).
There are three types of neurofibroma: localized,
diffuse and plexiform.
Localized neurofibroma is the most common form,
representing %90 of all cases.
The vast majority of localized neurofibromas are solitary and not associated with neurofibromatosis type 1 (3,4).
They arise from superficial cutaneous nerves,
however large deep seated nerves may also be affected.
They are slow growing,
painless lesions,
usually less than 5 cm in size at presentation.
Peak presentation is between 20 and 30 years of age with no sex predilection (5).
On Magnetic Resonance Imaging (MRI),
they are typically isointense to muscle on T1-weighted (T1W) images and slightly hyperintense to fat on T2-weighted (T2W) images with heterogeneous contrast enhancement (6).
On crosssectional MR images,
a “target sign” appearance may be seen on T2-weighted images which helps distinguishing neurofibromas from other benign soft tissue tumors,
especially from schwannomas (7).
In a minority of patients neurofibromas might transform into malignant nerve sheath tumors (8).
Although they can be seen anywhere,
foot is a rare localization.
Herein we present a case of neurofibroma deeply seated between the foot muscles.
Case Report: A 48 year old male patient admitted to our orthopedics clinic with right foot pain that has been occurring for 3 weeks.
There was no history of trauma or chronic illnesses.
On physical examination he was found to have tenderness and palpable fullness on the metatarsal region of foot.
Laboratory examination results including complete blood count,
erythrocyte sedimentation rate,
C-reactive protein value,
Rheumatoid Factor,
blood biochemistry,
liver and kidney function tests were normal.
Plain x rays of right foot taken in two directions revealed no abnormality (Figure 1).
MRI showed well-defined expansive soft tissue mass deeply seated between plantar muscles which was isointense with muscle on T1W images and hyperintense on T2W images (Figure 2).
No “target sign” was observed.
Contrast enhanced sequences demonstrated heterogenous enhancement of the soft tissue mass (Figure 3).
Given the clinical,
laboratory and radiological findings the mass was tought to be a schwannoma at first and differential diagnosis include neurofibroma.
The patient underwent surgery and the result of the pathological examination was neurofibroma.
Discussion: Usually associated with neurofibromatosis these tumors can present in patients without the disease.
Although neurofibromas are benign,
they can be a harmful soft tissue mass because they do have a small risk of transforming into malignancy.
Neurofibromas can also cause crippling pain and affect the body’s function.
Early diagnosis can help prevent nerve damage or deformity.