SEPs make up 4% of all plasma cell tumors and can occur in any site in the body, but are found mainly in the upper aerodigestive tract (UAD).

• 单独骨髓外浆细胞瘤佔所有浆细胞肿瘤的4%25，可能发生在身体的任何部位，主要发生于上消化呼吸道，发生于纵膈腔及胸壁者相当罕见。