Issues of morphological diagnosis and pathogenesis of tuberculosis

Tuberculosis remains a serious global problem of our time. The epidemiological situation regarding tuberculosis in the Russian Federation and in Moscow is quite favorable, however, many manifestations of diseases and morphological changes in tuberculosis require a serious approach to the timely diagnosis of the disease, especially intravital morphological verification of the process. The article outlines the main aspects of the pathogenesis of tuberculosis, including deep immunosuppression associated with HIV. A typical microscopic picture of tuberculosis inflammation is described with an algorithm for identifying the causative agent of tuberculosis in histological sections and cytological preparations, and species identification of mycobacteria in material from paraffin blocks. Attention is paid to the morphology of HIV-associated tuberculosis, which is characterized by the loss of signs of granulomatous inflammation in condition of deep immune suppression. The need for differential diagnosis of tuberculosis with many infectious and non-infectious granulomatous-necrotic processes is noted, which requires the morphologist to compare the cellular composition of granulomas, study perifocal tissue reactions and features of vascular damage, correctly assess the activity of inflammatory changes, etc. Attention is drawn to the features of the morphological diagnostic search in cases combined pathology of tuberculosis with other infectious diseases, incl. with Covid 19. Changes are difficult to analyze due to the combination of morphological manifestations of several diseases, each of which may have atypical microscopic manifestations, as well as the varying activity of several simultaneously occurring infectious processes.