Caseous necrosis

Caseous necrosis describes a form of biological tissue death. The dead tissue appears as a soft and white proteinaceous dead cell mass. Like most patterns of necrosis, no histological architecture is preserved - it is characterised by acellular pink areas of necrosis surrounded by a granulomatous inflammatory process. Frequently, caseous necrosis is associated with tuberculosis (TB).

When the hilar lymph node for instance is infected with tuberculosis and leads to caseous necrosis, it would appear to have a cheesy tan to white appearance, which is why this type of necrosis is often depicted as a combination of both coagulative and liquefactive necrosis.

However, in the lung, extensive caseous necrosis with confluent cheesy tan granulomas is typical. The tissue destruction is so extensive that there are areas of cavitation (also known as cystic spaces). See Ghon's complex.

Clinical Summary
A 70-year-old man was admitted to the hospital with a history of upper abdominal pain, anorexia, nausea, and general malaise, all of approximately three weeks' duration. His hospital stay was characterized by fever and severe respiratory distress. There were multiple densities in the patient's chest x-ray consistent with pneumonia and examination of a stained sputum specimen showed acid fast bacilli. Despite intensive therapy, the patient progressively deteriorated and died 14 days after admission.

Autopsy Findings
It was determined at autopsy that the patient suffered from pulmonary tuberculosis with widespread dissemination throughout the body. The left lung weighed 620 grams and the right lung 1230 grams. These were characterized by marked congestion and edema. In addition, multiple gray-white nodules ranging from pinpoint size up to 1 cm were diffusely distributed throughout the lung parenchyma.

Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology