Aim. Demonstration of clinical cases of plasmacytoma, both solitary and one of the manifestations of multiple myeloma. Materials and methods. A brief literature review on the diagnosis of bone and extramedullary plasmacytoma and clinical observations of various tumor options from the personal practice of the authors is presented. Results. Two clinical observations of the primary diagnosis of solitary plasmacytoma are presented. In one case, there was a bone tumor, in the other − an extramedullary tumor. In both observations, a generalization of the process was subsequently noted. Three clinical cases of primary diagnosis of multiple myeloma accompanied by the development of plasmacytoma are also presented. In two cases, there was a lesion of the bone marrow, in one – a multiple-focal form of the disease. In two situations, a non-secreting variant of multiple myeloma was diagnosed. The features of diagnosis and treatment were analyzed. Conclusion. In the diagnosis of focal forms of plasmacytoma (without lesions to the bone marrow and secretion), the leading role belongs to histological and immunohistochemical studies.