J Korean Orthop Assoc.  2016 Jun;51(3):266-271. 10.4055/jkoa.2016.51.3.266.

Tibial Schwannoma Mimicking a Popliteal Cyst

• Min KD
• Yoo JW
• Cho WI
• Hwang SH

• KMID: 2308589
• DOI: http://doi.org/10.4055/jkoa.2016.51.3.266

Abstract

Schwannoma is the most common benign tumor of peripheral nerves and usually appears on the trunk, head and neck, or extremities. A mass arising at popliteal fossa can be misdiagnosed as a popliteal cyst. We report on a rare case of a popliteal schwannoma mimicking a popliteal cyst in a 39-year-old female who showed a clinical presentation similar to that of a popliteal cyst. Diagnosis was delayed until ultrasonographic evaluation was performed due to its anatomical location, the same as that of a popliteal cyst. We describe the clinical significance and ultrasonographic findings of the schwannoma for initial differential diagnosis from a popliteal cyst.

Keyword

schwannoma; popliteal cyst; ultrasonography

MeSH Terms

Adult
Diagnosis
Diagnosis, Differential
Extremities
Female
Head
Humans
Neck
Neurilemmoma*
Peripheral Nerves
Popliteal Cyst*
Ultrasonography

Figure

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  Figure 1 Lateral X-ray of the right knee shows a round soft tissue shadow in the popliteal space.

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  Figure 2 Ultrasonographic findings showing a well-defined, hypoechoic oval shaped nodular mass filled with nonhomogeneous components (A) and tibial nerve fascicular continuity at its proximal end (B). (C) Compression of the popliteal vein was observed at the bottom of the mass.

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  Figure 3 Magnetic resonance imaging findings of the mass. Saggital T1- (A), T2- (B), and axial T2 contrast enhanced-weighted images demonstrating a well-marginated mass with hypointense (A), hyperintense (B), inner heterogeneous (C) signals, respectively.

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  Figure 4 Photograph of the right popliteal fossa mass at surgery, which confirmed a well-defined mass originating from the tibial nerve branch (A) and an enucleated mass, 5×4×3 cm in size (B).

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  Figure 5 Pathological diagnosis was schwannoma. (A) Tumor cells have ill-defined cytoplasm and nuclear palisading (H&E, ×400). (B) Positive result of immunohistochemical staining for S-100 protein (×200).

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