PMC8710498_01
Imaging views of the knee. (A) Anterior and lateral X-ray views showed the osteolytic changes (red arrows) in the patella. (B) Sagittal and transverse computed tomography (CT) images showed the decreased bone density (red arrows) in the patella, and tumor involvement inside the whole patella. (C) Sagittal magnetic resonance imaging (MRI) revealed a low signal in the T1-weighted image and a high signal in fat-suppressed T2-weighted image (red arrows). (D, E) Positron emission tomography-computed tomography (PET/CT) showed extremely intense focal uptake in the right knee joint and no focal uptake in other sites.
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X-ray examination revealed the decreased bone density, cortical bone discontinuity, slight swelling, and unchanged knee joint space of the right patella, which confirmed a pathologic fracture of the right patella ( Figure 1A ). Figure 1A ). Further workup was ordered, including computed tomography (CT) scan, magnetic resonance imaging (MRI), and positron emission tomography-CT (PET/CT). CT scan showed the tumor involvement inside the whole patella and the lesion with defining borders ( Figure 1B ). MRI revealed that the lesion had a decreased signal in the T1-weighted image (T1WI), as well as a high signal in fat-suppressed T2-weighted image (T2WI-FS) with surrounding soft-tissue swelling and fluid effusion in the articular cavity ( Figure 1C ). Figure 1D ). Further, a whole-body PET/CT scan showed extremely intense focal uptake in the right knee joint and no focal uptake in other sites ( Figure 1E ).
Histologic examination of the right patellar mass reveals the diffuse infiltration by atypical lymphocytes.
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Subsequently, the pathologic examination of the patella demonstrated the diffuse infiltration by atypical lymphocytes, which was highly pleomorphic ( Figure 2 ).
Surgical operation and post-operation follow-up. (A, B) The expansion of quadriceps femoris muscle and the residual support structure surrounding the patella was directly sutured after the patella was completely resected. (C-F) Postoperative functional examination demonstrated a satisfactory functional recovery of the patient.
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The surgical procedure demonstrated the involvement of the patella interior and no invasion of the surrounding tissue ( Figures 3A, B ). At the 1-year follow-up clinic visit, the patient had completed all therapy and achieved a satisfactory functional recovery ( Figures 3C-F ).