Healed Primary Complex

Definition: From the host's point of view, the residue of a successful encounter with the tubercle bacillus is a peripheral, rounded scar, less than 1 cm in diameter, in the lower half of the lung. Together with a similar scar in a hilar lymph node, it is known as the Ghon complex.

Peripheral part of the Ghon complex: These rounded scars occur subpleurally and are often calcified (blue area at arrow). Depending on the components present, they are designated fibrous, fibrocaseous, or fibrocalcific nodules. They usually show little or no inflammation.

The presence of multinucleated giant cells or active necrosis, however, indicates activity. This scar had scattered lymphocytes around it, but no multinucleated giant cells or necrosis.

Central part of the Ghon complex: A similar scar can often be found in a draining hilar lymph node.

Significance: The peripheral lesions are occasionally removed surgically for diagnosis of a solitary pulmonary nodule, or incidentally during the course of excision of another lesion. They are a routine autopsy finding in patients who have encountered the bacillus. In that situation, palpation of the pleural surface of the lower half of the lung is the best way to find them. Section of the associated hilar lymph nodes may show the central portion of the Ghon complex.

Results of special stains for organisms: When a fibrous, fibrocaseous, or fibrocalcific nodule is resected, special stains for acid fast and fungal organisms are routinely performed even if the nodule appears to be inactive, histologically. If the cause was mycobacterial disease, the stains are almost always negative, but if the granuloma had a fungal origin, the Gomori methenamine silver stain for fungi is frequently positive. The decision to treat a patient with organisms in a fibrotic granuloma depends on the immunologic status of the patient.

This subpleural nodule was removed from the lower lobe at the time of resection of a lung cancer. The fibrotic nodule has a heavy lymphoid infiltrate at the edge, but no multinucleated giant cells, granulomas, or necrosis were seen. A stain for acid fast organisms was negative, but the Gomori methenamine silver stain showed small yeast forms of histoplasma (right).

Active Lymph Nodal Disease

Definition: Tuberculous adenopathy is more common in progressive primary disease in childhood than in postprimary tuberculosis. However, it may be found in severe postprimary disease, as well as in immunosuppressed patients, especially those with AIDS.

Here, several hilar lymph nodes are partially or completely involved by tuberculosis. They are strategically placed to be able to compress or erode into vessels (upper arrow) or airways (A). The lower arrow indicates a focus of calcification.

The involvement of the lymph nodes shown here is more extensive than that seen as part of a healed Ghon complex. These nodes were part of an incompletely treated, chronic parenchymal infection. A healed central component of the Ghon complex is usually solitary and less than 1 cm in diameter.

Active tuberculosis may be associated with hilar and mediastinal adenopathy. Note the enlarged right paratracheal node with central low attenuation and the right prevascular node between the ascending aorta and superior vena cava. Adenopathy is more common in children and immunosuppressed patients than more immunocompetent hosts. Tuberculous adenopathy frequently shows central low attenuation indicating necrosis.

A rare, late complication of tuberculous lymphadenitis is broncholithiasis. The calcification that develops in the lymph node erodes into the airway as shown here. Broncholithiasis may present as chronic lithoptysis, hemoptysis, or airway obstruction. The stone can be localized by HRCT [1].

Reference

1. Galdermans D, Verhaert J, van Meerbeeck J, de Backer W, Vermeire P. Broncholithiasis: present clinical spectrum. Respir Med 1990; 84:155-156.

Clinical summary Granulomatous pneumoniaDiscussion

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