Primary cutaneous extramedullary plasmacytoma secreting lambda IgG.

An adult male was described, who developed a tumour on his left arm, which was diagnosed as a primary cutaneous extramedullary plasmacytoma after histopathological, electron microscopic and immunocytochemical studies. Further studies ruled out the presence of multiple myeloma, extramedullary plasmacytoma of another site, or paraproteinaemia/paraproteinuria. During a relapse of the tumour 2 1/2 years after initial treatment, a new immunocytochemical study demonstrated that the tumour cells expressed monoclonal lambda IgG at the intracytoplasmic level, an unusual finding.