A patient with extramedullary solitary tumor had progressive sensory motor neuropathy, generalized pigmentation of skin, pretibial edema and gynecomastia. Serological examination of this patient showed monoclonal IgA-lambda gammopathy. Histologically, the tumor was defined as an IgA (lambda type) positive extramedullary plasmacytoma by using peroxidase anti-peroxidase staining. The tumor was accompanied by angiofollicular lymphoid hyperplasia. Pathologically, it was recognized as an extramedullary plasmacytoma associated with Castleman's disease like changes, and was successfully treated by surgical resection, followed by irradiation.