Pulmonary tuberculoma

Pulmonary tuberculoma is a clinical form of tuberculosis in which a caseous-necrotic formation with a diameter of more than 12 mm forms in the lung tissue, separated from the adjacent lung tissue by a two-layer capsule.

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Epidemiology

Tuberculoma is detected in 2-6% of newly diagnosed patients with respiratory tuberculosis, primarily in adults aged 20-35 years. More than half of the patients are detected during control fluorographic examinations, since most of them do not have obvious clinical signs of the disease.

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Causes pulmonary tuberculomas

The development of tuberculoma occurs against the background of a hyperergic reaction of cellular elements of lung tissue to mycobacteria tuberculosis and increased activity of fibroplastic processes in the zone of tuberculous inflammation. The formation of tuberculoma can be facilitated by inadequate treatment of the disease, which leads to a longer preservation of the pathogen population in the affected area.

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Pathogenesis

In case of incomplete reverse development of tuberculous inflammation, resorption and reduction of the infiltrate size are combined with an increase in the volume of caseous-necrotic masses in its central sections. Such dynamics are observed in the presence of highly virulent strains of mycobacteria in the infiltrate, as well as with increased tension of general and local cellular immunity. A granulation layer appears around the centrally located zone of caseous necrosis, and collagen fibers are formed along its outer borders and a thin fibrous layer begins to form.

A small infiltrate with pronounced caseous-necrotic changes in the center can also form when several caseous foci merge. Such an infiltrate also undergoes encapsulation rather quickly and is transformed into a tuberculoma.

The tuberculoma capsule consists of two layers. The inner layer, formed by tuberculous granulations, surrounds the caseous core of the tuberculoma. The outer layer, represented by concentrically located fibrous fibers, separates the tuberculoma from the adjacent slightly changed lung tissue. A massive caseous core and a thin (1-1.5 mm), well-formed fibrous capsule are characteristic morphological features of the most common type of tuberculoma - caseoma. For the infiltrative-pneumonic type of tuberculoma, alternating areas of caseous necrosis with epithelioid-cell tubercles and poorly developed capsule are characteristic.

Tuberculomas that form from infiltrates and foci are usually called true. From a pathomorphological standpoint, several types of true tuberculomas are distinguished: solitary (homogeneous and layered) and conglomerate (homogeneous and layered).

A solitary homogeneous tuberculoma is represented by a round caseous-necrotic focus surrounded by a two-layer capsule. A conglomerate homogeneous tuberculoma consists of several small caseous foci united by a single two-layer capsule. In layered tuberculomas, the caseous core is surrounded by concentric layers of fibrous collagen fibers, which alternate with layers of caseous necrosis. This indicates a wave-like course of the process.

In many progressive tuberculomas, areas of destruction can be found that are formed as a result of the melting of caseous masses and their resorption by phagocytes. Such processes occur only in the peripheral sections; there are no blood vessels in the central sections of tuberculomas, and proteolytic enzymes and phagocytes do not penetrate into these sections. As a result, decay in the tuberculoma has a marginal location. When the tuberculoma capsule melts, conditions arise for communication between the decay cavity and the bronchus. In this case, the caseous masses are rejected into the lumen of the bronchus and the size of the decay cavity increases.

Various adverse effects that suppress cellular immunity and change the hormonal background in the body can lead to significant progression of tuberculoma with the development of caseous pneumonia or cavernous tuberculosis with subsequent transformation into fibrous-cavernous tuberculosis of the lungs.

The stationary course of this form of tuberculosis is characterized by the absence of perifocal infiltration and signs of decay in the tuberculoma. In the tissue surrounding the tuberculoma, changes caused by pneumofibrosis are visible. as well as dense foci without obvious signs of activity.

With a consistently regressive course of tuberculoma, caseous masses eventually become denser and fragmented, the size of the tuberculoma slowly decreases, and it gradually becomes saturated with calcium salts. A dense fibrous focus or a zone of limited pneumofibrosis may form in its place. Sometimes, with a regressive course of tuberculoma, caseous masses may be almost completely rejected, after which a small thin-walled cavity remains, the walls of which are the former capsule of the tuberculoma. Later, such a cavity most often scars. With involution of the tuberculoma, a few fibrous foci, cords formed by obliterated small vessels and bronchi are usually detected in the surrounding lung tissue.

A peculiar variant of tuberculoma is considered to be a filled cavern, which is called a false tuberculoma, or pseudo-tuberculoma. The blocked cavern gradually fills with necrotic masses, lymph and cellular elements and is transformed into a rounded, volumetric formation delimited from the surrounding tissue. The fibrous layer surrounding such a false tuberculoma is usually quite wide, and the caseous masses lack alveolar septa and other structural elements of the lung tissue.

The clinical course of tuberculoma can be progressive, stationary, or regressive.

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Symptoms pulmonary tuberculomas

The isolated nature of the lesion causes a low-symptom, often inapperceptive, chronic course of tuberculoma in many patients. Exacerbation usually occurs under the influence of unfavorable factors of the external and internal environment, which reduce the likelihood of limiting specific inflammation in the lung. Patients experience weakness, loss of appetite, weight loss, and sometimes an increase in body temperature to 37.5-37.8 °C. Chest pain associated with breathing, cough (dry or with a small amount of sputum) may occur. In rare cases, hemoptysis occurs. The results of a physical examination of the lungs depend on the size of the tuberculoma, its location, and the phase of the tuberculosis process.

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Diagnostics pulmonary tuberculomas

The main radiological syndrome in tuberculoma is a limited (focal) darkening, often located subpleurally, in the 1st, 2nd or 6th segments. There are small (diameter up to 2 cm), medium (diameter 2-4 cm) and large (diameter more than 4 cm) tuberculomas, which can be single or multiple.

A round, regular shape of darkening corresponds to a solitary tuberculoma. An irregular shape and a polycyclic outer contour are characteristic of a conglomerate tuberculoma. A cavity of decay is often detected, which is located eccentrically and can have a different shape. When caseous masses are rejected through the bronchus, the cavity of decay is located near the mouth of the draining bronchus.

The contours of the tuberculoma are usually clear. Blurring of the contours indicates perifocal infiltration, which appears during the progression of the tuberculoma. When a "path" to the root of the lung is also detected in the form of perivascular and peribronchial compactions with foci of seeding in the surrounding lung tissue.

The inhomogeneity of the shadow of a tuberculoma may be due to the heterogeneity of the caseous masses: the presence of fibrous strands, calcifications, and areas of destruction.

An important feature of the radiological picture of tuberculoma is the presence of a few polymorphic foci and pneumofibrosis in the surrounding lung tissue.

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