Objective: To explore the clinicopathological features, diagnosis, differential diagnosis and prognosis of extramedullary plasmacytoma (EMP). Methods: Twelve cases of EMP were collected and their clinical manifestations, histopathology, immunophenotypic characteristics and related molecular pathology were observed. Follow-up data were collected and published relevant literatures were reviewed. Results: There were 9 males and 3 females with an average age of 59.1 years. Patients showed more local symptoms. No immunoglobulin appeared in serum and urine. There were 7 cases of head and neck, 2 cases of lymph nodes, and one case of posterior mediastinum, testis and jejunum. Microscopically, the plasma-like cells were diffusely infiltrated and classified into grade 3 according to the degree of cell differentiation. The tumor cells were positive for CD38, CD138, CD79α, CD56, CyclinD1, MUM-1 and exhibit light chain restriction. The Ki-67 proliferation index averaged 35.8%. Three cases of Epstein-Barr virus-encoded small RNAs (EBER) were negative, and one case showed positive IgH gene rearrangement. Ten patients were followed up, 1 patient relapsed, 1 patient died. Conclusion: EMP is a rare plasmacytoid tumor that occurs outside of the hematopoietic tissue of the bone marrow and occurs frequently in older men. There are little immunoglobulin in serum and urine. The diagnosis focuses on the morphological characteristics of plasma-like differentiation, the immunophenotype of the plasma cell and the light chain restriction. The prognosis is good, and a minority may progress to multiple myeloma. Long term follow-up is required.