Presentation
Right orbital swelling and proptosis.
Patient Data
Right orbital superolateral expansile marrow infiltrative lesion eliciting abnormal signal and showing extra-osseous intra-cranial extra-dural and intra-orbital extra-conal components. The intra-cranial extra-dural component is indenting the right frontal lobe. While the intra-orbital extra-conal component is abutting the superior aspect of the globe. It elicits a high signal on T1 fat sat sequence and isointense signal on T2 WI with intense post-contrast enhancement.
Pathology after excision revealed plasmacytoma.
Bone marrow aspirate revealed normocellular marrow with 8% plasma cells.
Case Discussion
The patient had right orbital superolateral marrow infiltrative lesion. Differential possibilities include metastasis, plasmacytoma, or lymphoma. Excision and pathology revealed plasmacytoma. Subsequent bone marrow aspirate was normal. with low count plasma cells. No other lytic lesions on PET CT. This means this is a solitary bone plasmacytoma which represents an isolated form of multiple myeloma involving a solitary bone.
Solitary bone plasmacytoma differs from multiple myeloma by the presence of only one lesion (bone or soft tissue), normal bone marrow (<5% plasma cells), normal skeletal surveys, absent or low paraprotein, and absence of end-organ damage.
Solitary bone plasmacytomas usually progress to multiple myeloma in 3 to 5 years.