Endometrial tuberculosis. Light micrograph of tissue from the lining of the womb (endometrium) in a case of endometrial tuberculosis. Tuberculosis (TB) is a disease caused by infection with Mycobacterium tuberculosis bacteria. The bacteria are usually inhaled in water droplets, and can progress from the lungs to the lymphatic system, as well as to other body organs. Sites of infection (tubercles) are the solid pink areas at left and right