Synovial metastasis from lung cancer

Abstract

Intraarticular masses are infrequently encountered in clinical practice; however, the differential diagnosis can be broad. Neoplasia, both benign and malignant, and proliferative processes are the most common etiologies. We present a case of metastatic disease in the synovium in a patient with a history of lung cancer. Lung carcinoma is the most common primary malignancy to metastasize to synovial tissue, and the knee joint is the most common joint to be affected.

Figure 1

An unenhanced axial T1-weighted image at the level of the intercondylar notch demonstrates the knee joint space and synovium replaced by an intermediate soft tissue intensity mass (green arrowheads) with thin septations.

Figure 2

A sagittal fat-saturated T2-weighted image at the same location as the proton-density image demonstrates a mass (outlined in orange arrowheads) with associated edema, a small effusion or cystic region (yellow arrow), and distending joint space. The blue arrowhead points to a pathologic lymph node. Again, there is a minor edema signal in the tibial plateau and intercondylar notch but no aggressive subchondral osseous extension.

Figure 3

A sagittal proton-density image demonstrates a mass (blue arrowheads) interdigitating throughout the knee joint surrounding stretched yet intact cruciate ligaments (red arrows). There is no evidence of osseous or extraarticular extension of the mass.

Figure 4

A precontrast fat-saturated T1-weighted image at the level of the intercondylar notch shows persistence of the signal in the mass (orange arrowheads) on fat-saturated imaging, proving a lack of fat content and the presence of proteinaceous material.