Multiple primary cutaneous plasmacytomas

Cutaneous plasmacytoma is an uncommon tumor and is mostly seen in the context of end-stage multiple myeloma. Only 20 cases of primary cutaneous plasmacytoma have been documented. A significant proportion of these patients went on to develop systemic disease with a poor prognosis. In a number of patients, however, the abnormal clone of plasma cells may arise in the skin and never progress to multiple myeloma involving the bone marrow.

We describe a patient who developed multiple primary cutaneous plasmacytomas after a possible insect bite reaction. The monoclonality of the tumor cells is demonstrated using immunohistochemical techniques. He has been treated vigorously with chemotherapy and local radiotherapy and remains well 3 years after diagnosis. Bone marrow has been harvested for use as an autologous bone marrow transplant in the event of systemic relapse.

Unlike previous reports of this rare entity, this case documents the monoclonality of tissue plasma cells with immunohistochemical techniques. As cutaneous plasmacytomas have been reported with an early significant mortality, unlike extramedullary plasmacytomas elsewhere, we have advocated combination chemotherapy and cryopreservation of uninvolved bone marrow for future autologous bone marrow transplantation should systemic myelomatosis develop in the patient.