Cutaneous plasmacytomas in myeloma. Relationship to tumor cell burden.

Solitary cutaneous plasmacytomas may occur as benign tumors that are confined to the skin, whereas multiple lesions are generally associated with systemic plasma cell disease. Cutaneous plasmacytomas developed in two patients with documented multiple myeloma; this development occurred late in the course of their disease at a time when their systemic plasma cell tumor burden was large-approximately 3 kg in mass, which represented 2 to 3 x 10(12) cells. The occurrence of cutaneous plasmacytomas in patients with multiple myeloma is generally late in the course of the disease and should be considered as a bad prognostic sign.