This article is devoted to such a benign acquired condition as postsplenectomy splenosis, which is often incorrectly interpreted as a primary malignant tumor or secondary (metastatic) tumor process. The article provides a modern definition of the concept of «splenosis», examines the main mechanisms of autotransplantation of splenic tissue, indicates the most typical localizations of splenosis foci, provides the timing of the onset of splenosis, considers possible clinical manifestations and potential complications of this condition, discusses modern approaches to diagnostics, differential diagnostics of splenosis, tactics of management and treatment of such patients in detail, and also provides own author’s clinical observation of disseminated spontaneous postsplenectomy splenosis mimicking disseminated malignant tumor process. The feature of this clinical case is the presence of hereditary microspherocytosis (congenital microspherocytic hemolytic anemia, Minkowski-Chauffard disease) in the patient, which served as the reason for splenectomy. The article is illustrated with original computed tomography and magnetic resonance imaging.