Skin lesions in Waldenström's macroglobulinaemia. Characterization of the cellular infiltrate.

A patient with Waldenström's macroglobulinaemia presenting with numerous red or brownish-red, round, papulous lesions of the skin is reported. Skin biopsy revealed a massive infiltrate of immature lymphatic cells of the dermis down to the subcutaneous fat. Approximately 80% of these cells were positive for intracellular IgM and kappa light chains as shown by the immunoperoxidase method. This finding established the skin lesions as part of Waldenström's macroglobulinaemia.