Ghon's complex is a pathological entity caused by the the progression of tuberculosis, an infectious respiratory disease. Specifically, the Ghon's complex is a combination of the Ghon's focus (area of initial infection by airborne bacillus) and a lymphatic lesion. Approximately two to three weeks after the Ghon's focus has developed, the area undergoes caseous necrosis (cheeselike). Free tubercle bacilli, or bacilli within macrophages drain out from the area towards the affected lungs' lymph nodes. It is in this location, at the lymph nodes, that the bacilli will form caseous granulomas. This, in combination with the initial area of infection, will make up the Ghon's complex. Typically these areas heal with calcification visible on chest X-ray, with the two causes virtually indistinguishable.
See Ghon focus
Porth, Carol Mattson. Pathophysiology:Concepts of Altered Health States, 7th edition. Philadelphia: Lippincott Williams & Wilkins, 2005.