This week’s case is a 13-year-old Staffordshire Terrier with a palpable pelvic mass.
FindingsThere is extensive bone lysis and expansion of the left ischium and ilium. The cortex is destroyed, and the mass appears to extend very near to the left acetabulum.
Ten months post radiation therapy, the mass has reduced in size by half. The margins are very well circumscribed and well-mineralized. A coarse, disorganized trabecular pattern remains.
Differential DiagnosisAggressive bone lesion
- primary bone tumor
- fungal osteomyelitis
- (metastatic neoplasia)
DiagnosisPlasma Cell Tumor
DiscussionThis aggressive bone lesion was not surgically resectable and was treated with a total dose of 48Gy in 16 3Gy fractions using 10MV photons. The external mass resolved, and the pelvic bones returned to a near-normal shape and density.
Solitary plasma cell tumors are rare and are most commonly reported in the axial skeleton. They do not produce immunoglobulins as multiple myeloma does. Plasma cell tumor may also progress to multiple myeloma.