Clinicohistopathological features and outcome of cutaneous and systemic plasmacytosis in 21 Chinese cases: A retrospective study.

Background Cutaneous and systemic plasmacytosis is a rare disorder predominantly observed in individuals of Asian descent. The aetiology, treatment modalities, and prognosis of this condition remain unclear. Objective To describe the clinicohistopathologic features and outcomes in patients with cutaneous and systemic plasmacytosis. Methods We analysed data from 21 patients treated at West China Hospital of Sichuan university from 2011 to 2022. Results All patients exhibited characteristic reddish-brown patches or plaques, primarily located on the trunk, head, face, and neck, with one patient also showing affected soles. Lymphadenopathy was present in 38.9% (7/18), and bone marrow involvement in 100% (7/7). Polyclonal immunoglobulinemia appeared in 91.67% (11/12), with elevated IgG4 in 87.5% (7/8) and IL-6 in 83.3% (5/6). Monoclonal gene rearrangements were observed in 54.5% (6/11) of patients. Over 5.3 years, 11.1% (2/18) partially remitted, while 44.4% (8/18) progressed, with four developing multicentric Castleman disease. Limitations This is a retrospective evaluation with a small number of cases; further prospective studies are warranted to support our inferences. Conclusions Cutaneous and systemic plasmacytosis often follows a chronic, progressive course. Our findings indicate an overlap in pathological features with cutaneous marginal zone B-cell lymphoma (MZBCL) and an association with IgG4-related disease. Additionally, some cases developed into multicentric Castleman disease. Currently, no effective treatment regimen has been established for this condition.