Sphenoid sinus localization of multiple myeloma revealing evolution from benign gammopathy

Plasma-cell neoplasms of the head and neck include extramedullary plasmacytoma and solitary plasmocytoma of bone or may represent a local manifestation of multiple myeloma. Involvement of sphenoid sinus has been rarely reported in multiple myeloma.

We present the case of a 77-year-old man with a 3-year-history of benign monoclonal IgG-lambda gammopathy who developed left sixth-nerve palsy and malaise.

Computed tomography scan and magnetic resonance imaging scan disclosed a large soft-tissue mass of the sphenoid sinus with bone destruction. Sphenoid sinus biopsy revealed an IgG monoclonal plasma cell neoplasm. Diagnosis of multiple myeloma stage IA was then established.

Diagnosis of plasma-cell neoplasm should be considered in sphenoid sinus tumors and depends upon histologic examination. This case enlightens the relationships between monoclonal benign gammopathy and plasma-cell neoplasms of the head and neck which constitute a continuum of B-cell lymphoproliferative disorders.