Gon Focus

Gon Focus (Ghon), or primary focus, denotes the primary tuberculous affection, i.e., that focal change in tissue which arises at the site of primary introduction of the tubercle bacillus into the organism. The name G.o. is connected with the name of the pathologist Professor Ghon from Prague, who in 1912 first gave a detailed patho-anatomical characterization of the indicated change. Since in the vast majority of cases primary infection with tuberculosis occurs aerogenically and in childhood, the G.o. in the active state is most often found in the lungs of children. Macroscopically, such a G.o. has the appearance of a cheesy focus, ranging in size from a pinhead to a cherry, located under the pleura of one or another part of the lungs (without preference for the apices). Microscopically, in the central part of the focus, a picture of tuberculous pneumonia is found, and along the periphery, a zone of tuberculous granulation tissue and tubercles. Almost as a rule, the G.o. is accompanied by tuberculous involvement of the lymphatic pathways leading from it to the hilum of the lung, and cheesy tuberculosis of the corresponding lymph nodes, which together are designated as the tuberculous primary complex. In most cases, the G.o. undergoes scarring, and then there remains a caseous mass surrounded by a thin, free from coal pigment connective tissue capsule, in which bone tissue usually subsequently forms. By these signs, the healed G.o., or focus of primary affection, differs from healed foci of secondary tuberculosis. Healed G.o. are found in 90-97% of all adult cadavers.