Patella plasmacytoma: An unusual localization


  • Conflict of interest: Nothing to report.

In July 2010, a 66-year-old woman presented with pain, edema, and ankylosis of the left knee. She had a nonsecretory multitreated multiple myeloma since 2002, relapsing in October 2009, and treated with Bortezomib, Dexamethasone, and Cyclophosphamide. Blood count, renal function, and free light chains assay were normal. The X-rays of knees did not show pathological fractures. However positon emission tomography scan (PET-scan) showed hyperfixation of the left patella (Image 1) (top views). On resonance magnetic imagery, there was a lesion on the lower part of the kneecap with fat and adjacent loft tissue infiltration and a cortical injury (bottom views). Following a needle biopsy, the diagnosis of plasmacytoma was made: histopathological examination found tumoral cells which were CD138 and CD56 positive. Symptoms improved with radiotherapy and after chemotherapy with Revlimid, Anthracyclin, and Dexamethasone was initiated.

Osteolytic lesions during multiple myeloma occur predominantly in axial skeleton (skull, spine, rib cage, and pelvis) and the proximal areas of the arms and legs [1]. Lesions are generally diagnosed by standard radiography. PET-scan is not recommended for routine use in the management of the myeloma patients [2], although this technique may be useful in selective cases like our patient.1

Illustration 1.

Positon emission tomography views (top) of legs (sagittal section on the left and frontal on the center) and knees (transversal section on the right); resonance magnetic imagery views (bottom) of knee (T1 sequence on the left and T2 on the center and the right). [Color figure can be viewed in the online issue, which is available at]