Abstract：
We report a rare case of spontaneous regression (SR) in an elderly untreated patient with multiple solitary plasmacytoma (MSP). Diagnosis of MSP was confirmed through surgical resection of the left nasal cavity mass and subsequent biopsy of the right humerus. The patient was considered ineligible for chemotherapy due to poor performance status. At 3-month post-diagnosis, the patient\'s condition worsened with deteriorating bone lesions and emergence of a new serum monoclonal protein. However, these clinical findings completely disappeared at 6 months, and positron emission tomography-computed tomography at 1 year confirmed complete metabolic remission. Notably, peripheral blood lymphocyte counts were inversely correlated with tumor progression and remission. Pathological re-evaluation of the initial biopsy specimens revealed programmed cell death protein 1 (PD-1) expression in tumor-infiltrating CD8+ T cells. In addition, tumor cells were infected with Epstein-Barr virus (EBV) but were negative for programmed cell death ligand 1 (PD-L1) expression, which is the most potent immune escape mechanism in tumor cells. While the mechanism underlying SR remains unclear, our findings suggest that host immune response as well as EBV infection may contribute to SR. Further studies are needed to elucidate the clinicopathologic mechanisms of tumor regression in plasma cell neoplasms.
摘要：
我们报告了一例罕见的多发性孤立性浆细胞瘤（MSP）老年患者的自发性消退（SR）病例。通过手术切除左鼻腔肿块和随后的右肱骨活检证实了MSP的诊断。由于表现状况不佳，该患者被认为不适合接受化疗。诊断后3个月,随着骨病变的恶化和新的血清单克隆蛋白的出现，患者的病情恶化。然而,这些临床发现在6个月时完全消失，1年时正电子发射断层扫描-计算机断层扫描证实代谢完全缓解。值得注意的是,外周血淋巴细胞计数与肿瘤进展和缓解呈负相关。初始活检标本的病理重新评估显示，肿瘤浸润性CD8T细胞中的程序性细胞死亡蛋白1（PD-1）表达。此外,肿瘤细胞感染EB病毒（EBV），但程序性细胞死亡配体1（PD-L1）表达阴性，这是肿瘤细胞中最有效的免疫逃逸机制。虽然SR的潜在机制尚不清楚，我们的研究结果表明，宿主免疫反应以及EBV感染可能与SR有关。需要进一步的研究来阐明浆细胞肿瘤肿瘤消退的临床病理机制。
