Pigmented villonodular synovitis of the cervical spine: case report and review of the literature

Abstract

Pigmented villonodular synovitis (PVNS) is an uncommon, benign, but locally aggressive lesion characterized most commonly by synovial proliferation of the appendicular large joints, but occasionally involving a bursa or the tendon sheath. PVNS of the spine is rare, typically involving the posterior elements. The lytic radiographic appearance and fludeoxyglucose avidity of PVNS may mimic malignant bone lesions, including metastatic disease or myeloma. On T ₁ and T ₂ weighted, and gradient recalled echo MRI sequences, the low signal intensity may mimic giant cell tumour of the bone, gout or synovial amyloid deposits, thus posing a diagnostic dilemma for the imagers and the treating clinicians. We present a pathologically confirmed case of PVNS of the cervical spine in a 49-year-old female, detailing her imaging work-up, describing histopathological correlation and highlighting the lesion location and involvement of the joint space as useful imaging discriminators for diagnosing PVNS of the cervical spine.

Figure 1.

MRI of a 49-year-old female with pigmented villonodular synovitis of the cervical spine. (a) Axial T ₁ weighted imaging without intravenous contrast demonstrates a heterogeneously hypointense trans-spatial mass (white open arrows) involving the dens and right lateral mass of C2, the anterior arch and right lateral mass of C1, and the prevertebral space. (b) The mass is markedly hypointense on T ₂ weighted imaging. (c) On sagittal contrast-enhanced fat-suppressed T ₁ weighted image, the lesion demonstrates faint, heterogeneous enhancement. There is no epidural extension of tumour.

Figure 2.

CT imaging of a 49-year-old female with pigmented villonodular synovitis of the cervical spine. (a) A contrast-enhanced CT scan reveals a lytic, heterogeneously enhancing, soft-tissue density mass (black solid arrow) involving the C1 and C2, extending ventrally into the prevertebral component of the perivertebral space (black open arrow). The anterior displacement of the right parapharyngeal space is noteworthy (black arrowhead), as expected from a mass originating in the prevertebral space. (b) Axial bone algorithm NECT demonstrates the lytic lesion (white solid arrow) involving the C1 and C2, including its involvement of the dens (white arrowhead). The sharp zone of transition and thin, sclerotic margins are noteworthy features typically associated with benign, slow-growing lesions. No matrix mineralization is seen. (c) Coronal reconstruction of bone algorithm NECT clearly demonstrates that the lesion is centred about the atlantoaxial joint (white open arrow), a critical diagnostic feature establishing this to be a tumour of synovial origin. NECT, non-contrast-enhanced CT.

Figure 3.

FDG-PET/CT imaging of a 49-year-old female with pigmented villonodular synovitis of the cervical spine. (a) Fused axial FDG-PET/CT image demonstrates the cervical spine lesion to be markedly FDG avid. (b) Coronal FDG-PET image demonstrates the C1/C2 lesion (white solid arrow), but there are no other suspicious foci of FDG uptake. Although seen with malignancy, FDG avidity is a marker of metabolic activity and is a non-specific finding that can also be seen with infectious, inflammatory and metabolic lesions. FDG, fludeoxyglucose; PET, positron emission tomography.

Figure 4.

CT-guided trans-facial biopsy images of a 49-year-old female with pigmented villonodular synovitis of the cervical spine. This composite image of three contiguous axial CT images (left = cranial, right = caudal) was obtained during the procedure. This minimally invasive biopsy technique can be performed under moderate sedation in an outpatient setting, avoiding the morbidity and expense of an open biopsy. Pre-procedural consultation with the oncologic surgeons is recommended in order to prevent potential contamination of the planned surgical approach in the event of inadvertent seeding of the biopsy tract with the tumour.

Figure 5.

Biopsy specimen of a 49-year-old female with PVNS of the cervical spine. Haematoxylin and eosin (100 × magnification) reveals (a) multinucleated giant cells (black solid arrows), foamy macrophages (black open arrows), and (b) pigmented macrophages (black arrowheads), which are the typical cellular constituents of a PVNS lesion but can also be seen within the solid component of an aneurysmal bone cyst, giant cell tumour of the bone or brown tumour of the bone. Definitive diagnosis of PVNS requires correlation with clinical features and imaging findings, as illustrated in this case. PVNS, pigmented villonodular synovitis.

Figure 6.

Biopsy specimen of a 49-year-old female with PVNS of the cervical spine. CD68 stain (40 × magnification) demonstrates that the majority of the cells are of histiocytic origin, typical of PVNS. PVNS, pigmented villonodular synovitis.

Figure 7.

Treatment changes in a 49-year-old female with pigmented villonodular synovitis of the cervical spine. Non-contrast-enhanced CT scan performed pretreatment (a) and 3 months following the initiation of imatinib mesylate therapy (b) reveals subtle reduction in the lesion size, best appreciated in the prevertebral component of the perivertebral space. The reduction in soft-tissue density mass with a more normal contour of the right parapharygeal space (white solid arrow) on post-treatment imaging is noteworthy.