[Gross spreading multiple extramedullary plasmacytomas to the skin in the terminal stage of multiple myeloma]

A 71-year-old woman with an 8-year history of IgG-kappa type multiple myeloma was admitted because of severe lumbago and bone destruction. Her serum IgG level was elevated to 5,565 mg/dl at admission. Despite treatment with doxorubicin, vincristine, dexamethasone, melphalan and interferon-alpha, the response was transient. Nine months later, multiple skin nodules appeared on her chest, abdominal wall and right thigh accompanied by elevation of the serum IgG level. Response to combination chemotherapy with cyclophosphamide, ranimustine, vincristine and prednisolone was also transient. The skin tumors on the bilateral thighs, especially on the left side, acquired chemotherapy resistance and gradually enlarged. Although the serum IgG level was maintained by chemotherapy within the range 1, 790-2,676 mg/dl, the skin tumors on the left thigh had spread very rapidly and appeared "rock-like". The enlarged tumors caused necrosis with erosions and oozing hemorrhage. A skin biopsy from the tumors on the left thigh showed plasmacytoma in which infiltration of large anaplastic plasma cells was observed. The patient died of sepsis 8 months after the skin tumors initially developed. This is a very rare case of multiple myeloma in which multiple large plasmacytomas of the skin developed and grew aggressively at the terminal stage after a long-term indolent course.