CASE 14184 Published on 16.01.2017

Peripheral schwannoma mimicking a bone tumour


Musculoskeletal system

Case Type

Clinical Cases


Roque Oca Pernas1;
Ana Navas Cañete2

Department of Radiology, Basurto University Hospital, Bilbao (Spain)1, and Leiden University Medical Center, Leiden (The Netherlands)2


44 years, male

Area of Interest Musculoskeletal system ; Imaging Technique MR, CT
Clinical History
A 44-year-old male patient presented with a history of several months of mechanical left shoulder pain. Physical examination showed preserved range of motion and muscle strength. The patient's past medical history was unremarkable.
Imaging Findings
Anteroposterior radiography revealed a well-defined lytic lesion affecting the scapula. The lesion showed a narrow transition zone with a thin sclerotic rim. No cortical destruction, periosteal reaction or matrix formation was observed. (Figure 1)
Magnetic Resonance Imaging (MRI) examination confirmed a solid, round and very well-defined soft tissue mass (3.5 x 2.8 x 2.4 cm) with epicentre in the spinoglenoid notch. There was also large remodelling of the underlying scapula that preserved a rim of very thin cortical rest.
The lesion had an intermediate signal intensity on T1-weighted images (WI) (Figure 2), hyperintense on the T2-WI (Figures 3) and an homogeneous enhancement after administration of Gadolinium (Figure 4).
A close relationship between the tumor and the suprascapular nerve was observed, but contiguity of both structures was not clearly shown (Figure 2).
There was no evidence of muscle atrophy, fatty infiltration or oedema suggesting denervation.
A CT-guided biopsy yielded the diagnosis of schwannoma (Figure 5).
Solitary benign peripheral nerve sheath tumours may be subdivided into schwannomas (neurilemmoma) and neurofibromas.
In up to 90% of the cases, both schwannomas and neurofibromas correspond to solitary lesions not associated with neurofibromatosis type 1. On the other hand, Neurofibromatosis type 1 presents almost invariably multiple neurofibromas, with visceral and deep nerve involvement and an increased risk of malignant transformation.
Schwannomas are composed primarily of Schwann’s cells and they are eccentrically located in relation to the involved nerve, presenting a true capsule composed of epineurium; they can be generally separable from the underlying nerve fibres.
In contrast, neurofibromas are centrally located, rarely encapsulated, and cannot be separated from the nerve [1, 2].

Schwannomas affect patients between 20–40 years old, and represent approximately 5% of benign soft-tissue neoplasms. They usually appear as a painless slow-growing soft-tissue mass, and symptoms may initiate when the lesion become large enough to compress the adjacent nerve [1].

MRI features of schwannomas consist of iso or low-signal-intensity lesions on T1-WI, high-signal-intensity lesions on T2-WI, and avid contrast enhancement.
The lesion generally shows fusiform shape oriented longitudinally and with tapered ends contiguous to the nerve of origin.
The lesion may show a characteristic “target sign” on T2-WI, with a central hypointense region, or the “split-fat sign” that represents a rim of fat surrounding the margins of the nerve sheath tumour, especially when it has an intermuscular location.
Imaging findings in many cases do not allow differentiation between schwannomas and neurofibromas, and the fusiform shape, the “split-fat sign”, and the “target sign” can be seen in both [3].
When the schwannomas are in close relation to a bone, it is often difficult to determine whether it is a soft tissue schwannoma involving the bone or an intraosseous schwannoma involving the surrounding soft tissues [4], but this last is less frequent. In this patient the tumour causes secondary remodelling of the bone due to the slow growing pattern.

Surgical excision is the treatment of choice for schwannomas, and the lesion is usually separable from the native nerve allowing the preservation of the rest of the nerve fibres and their function. Recurrence is rare and malignant transformation is extraordinarily unusual [1].

Take Home Points:
Soft tissue schwannoma may debut with the appearance of a benign bone solitary lesion due to its proximity to bones and its slow-growing pattern. A peripheral nerve sheath tumor may be included in the differential diagnosis of any well-defined mass in close relation to a nerve.
Differential Diagnosis List
Schwannoma of a branch of the suprascapular nerve mimicking a bone tumor.
Simple bone cyst
Giant cell tumor
Malignant peripheral nerve sheath tumour
Soft tissue sarcoma
Final Diagnosis
Schwannoma of a branch of the suprascapular nerve mimicking a bone tumor.
Case information
DOI: 10.1594/EURORAD/CASE.14184
ISSN: 1563-4086