Expression of syndecan-1 is a sensitive marker for cutaneous plasmacytoma

Cutaneous plasmacytoma is a well-recognized, yet infrequent, occurrence in multiple myeloma (MM). There are limitations in the morphologic assessment, and as such, the diagnosis presents some difficulty, particularly with the plasmablastic type.

Pathology reports of 2357 patients with a diagnosis of MM were reviewed. Twenty patients yielded a total of 25 plasmacytomas, 10 of which were analyzed for syndecan-1 immunoreactivity. Bartl grade of bone marrow and cutaneous plasmacytoma was compared and immunoglobulin secretory status of the patients was assessed.

The incidence of cutaneous plasmacytoma was found to be 1 in 118 patients with MM. Immunoglobulin secretion was found to be predominantly IgG. There was a trend for the plasmacytoma Bartl grade to be equal to or greater than that of the corresponding bone marrow Bartl grade, suggesting a more aggressive phenotype in the metastatic lesion.

Syndecan-1 was found to be a sensitive marker for plasmacytomas, independent of cytologic differentiation.