Induction of cutaneous plasma cell tumor as a complication of adjuvant immunotherapy with methanol extraction residue of bacillus Calmette-Guérin.
Methanol extraction residue (MER), a cell wall fraction of bacillus Calmette-Guérin, has been reported to exhibit immunomodulating properties which permit its successful use as an adjuvant of immunotherapy in cancer patients. Its beneficial immunostimulatory effects are generally thought to be due to nonspecific stimulation of cell-mediated immunity. Little attention has been focused on its humoral stimulating properties. A case is presented of a patient undergoing treatment with adjuvant immunotherapy with MER for malignant lymphoma who developed a cutaneous plasma cell tumor at the injection site of the drug. This complication may represent the result of enhanced humoral immunity induced by the MER treatment. The development of a cutaneous plasma cell tumor must be added to the list of known MER toxicities, and may constitute an indication for the discontinuation of treatment with this agent.