ORBITAL PLASMACYTOMA REVEALING MULTIPLE MYELOMA: CASE REPORT

Multiple myeloma (MM) is a malignant hematologic disorder in which orbital localization is exceptional (< 1%). We report the case of an orbital mass revealing multiple myeloma with an atypical radiological semiology. Contrary to classic descriptions, computed tomography (CT) showed integrity of the bone walls without bone lysis, thus simulating a lymphoproliferative process. However, magnetic resonance imaging (MRI) demonstrated a soft tissue mass with frank hyperintensity on diffusion-weighted imaging (DWI), reflecting tumor hypercellularity. The diagnosis was confirmed by histopathological and immunohistochemical examination showing plasmacytic infiltration with kappa monotypia, consistent with systemic multiple myeloma after biological workup. This case emphasizes that the absence of bone lysis does not exclude a plasmacytoma and recalls the importance of systemic evaluation in the presence of any solid orbital mass.