The 4th case of plasma cell neoplasm associated with a hypereosinophilic syndrome is described and compared with the previous reports. Hypereosinophilia in the present patient displayed some borderline traits with eosinophilic leukemia. Myeloproliferative disorders of the eosinophilic line often present as a precancerous state, but sometimes they seem to acquire malignant independence. In our patient the occurrence of a plasmocytoma with a dramatic course leads to suspect an underlying complex genetic aberration.