Presentation
Chronic painless, dorsal forearm mass.
Patient Data
Well-circumscribed soft tissue nodule identified within the extensor compartment of the distal forearm, between the extensor carpi ulnaris and extensor DTT minimi muscles, close the myotendinous junction. It has characteristics which would be most suggestive of a benign peripheral nerve sheeth tumor (well-circumscribed borders, well-defined thin increased T2 signal intensity rim surrounding the margin of the lesion, central cystic degeneration changes, split fat sign).
No aggressive features are identified to suggest malignant peripheral nerve sheath tumor (such as; irregularity of the lesion margins, surrounding soft tissue edema, surrounding postcontrast enhancement or a mean ADC value less than 1.0 on the diffusion-weighted sequences).
Case Discussion
One year follow up showed no significant interval change in the benign-looking soft tissue mass.
This case demonstrates classic findings of a peripheral nerve sheath tumor on MRI.
The combination of the above described MRI findings represents a neurogenic origin of the tumor and the lack of multiple malignant traits makes benign peripheral nerve sheath tumor the most likely the diagnosis.
Imaging alone is not enough to distinguish between schwannoma and neurofibroma, and can only be differentiated by histopathology.
The patient is not considering surgical intervals currently given the stability of the mass and lack of symptoms.