Secondary and primary pulmonary lymphomas
Secondary involvement of the lung parenchyma in lymphomas is observed significantly more often than primary involvement. The risk of detecting pulmonary nodules increases as the disease progresses or when relapses occur after treatment.
Hodgkin lymphoma (HL) involves the lung tissue three times more frequently than non-Hodgkin variants. At the same time, it is almost always accompanied by visible enlargement of intrathoracic lymph nodes. Isolated pulmonary involvement is more typical of non-Hodgkin lymphomas (NHL). An important nuance: if the patient previously received radiation therapy to the lung roots and mediastinum, a relapse confined solely to the lung tissue is possible with any type of lymphoma.
Primary lymphomatous involvement is extremely rare. The most frequent variant is MALT lymphoma (low-grade B-cell lymphoma), which originates from bronchus-associated lymphoid tissue. The tumor is usually located in the distal parts of the bronchial tree, in areas of bifurcation. The second most frequent is lymphomatoid granulomatosis (lymphomatoid granulomatosis), an angiocentric high-grade malignant lesion. Primary pulmonary Hodgkin lymphoma is considered a casuistic rarity.
Radiological patterns of lymphomas
The radiological picture of lymphomatous infiltration is highly variable. The most typical manifestations are:
- Areas of consolidation (consolidation), visually mimicking ordinary pneumonia. They frequently contain air bronchograms (air bronchograms).
- Multiple pulmonary nodules (pulmonary nodules), located subpleurally or within the parenchyma.
- Reticular or miliary changes (less common), which are difficult to distinguish on images from lymphangitic carcinomatosis.
In lymphomas, areas of consolidation often originate from the lung roots or mediastinum, ignoring the boundaries of anatomical lobes and segments. This is explained by the direct spread of tumor masses from affected lymph nodes. MALT lymphomas are characterized by multifocal or single foci of consolidation with pronounced air bronchograms; meanwhile, tissue breakdown (cavitation) or calcification is extremely rare, and pleural effusion is atypical.
Associated findings and diagnostic challenges
A frequent companion of pulmonary lymphomas (except for the MALT variant) is pleural effusion (pleural effusion). As a rule, it is unilateral and combined with massive intrathoracic lymphadenopathy. If effusion persists after mediastinal irradiation, its cause is more often lymphatic drainage blockage or venous compression rather than direct tumor involvement of the pleura.
Lobar atelectasis occurs infrequently and is usually associated with endobronchial tumor growth. Compression of bronchi by enlarged lymph nodes from the outside is atypical—lymphomatous masses tend to encase structures (encasement) rather than obstruct their lumen.
The main difficulty for the radiologist is the differentiation of the tumor process from infection. Due to immunodeficiency, inflammatory changes in the lungs present atypically; therefore, precise verification of the diagnosis in many cases requires a biopsy.
Pulmonary involvement in leukemias
Leukemic infiltration of the respiratory organs is detected at autopsy in the majority of deceased patients, but clinically it is frequently asymptomatic. If a patient with leukemia develops pronounced respiratory disorders, their cause is more likely a superimposed infection, hemorrhage, or pulmonary edema.
On imaging, infiltration can manifest as bilateral reticulation, ground-glass opacity (ground-glass opacification), small nodules, and areas of consolidation. T-cell leukemias can cause massive mediastinal adenopathy, which regresses phenomenally fast during therapy. In patients with myeloid leukemia, chloroma (granulocytic sarcoma)—a specific greenish thickening of the pleura—is occasionally encountered.
A special life-threatening condition is leukostasis in acute myeloid leukemia with extreme leukocytosis (over 100,000 cells per 1 mm³). The lung microvessels become clogged with cells, leading to severe dyspnea. The chest radiograph may remain normal or reflect developing pulmonary edema (pulmonary oedema).
An important diagnostic rule for Hodgkin lymphoma: if a pulmonary opacity is detected on an image, but the lung roots and mediastinum are not enlarged (and have not previously undergone radiation therapy), it is extremely unlikely to be a manifestation of lymphoma. Look for infection first.
Class and exam questions
Can non-Hodgkin lymphoma present with isolated pulmonary involvement without lymphadenopathy?
Yes, unlike Hodgkin lymphoma, isolated pulmonary tissue involvement is quite common in non-Hodgkin lymphomas.
How does MALT lymphoma differ from classic pneumonia on CT?
Although MALT lymphoma also presents with areas of consolidation containing air bronchograms, it progresses extremely slowly (over years), rarely causes pleural effusion, and lacks acute infectious clinical presentation.
Why does dyspnea occur in leukostasis even if chest X-rays show no massive infiltrates?
At ultra-high leukocyte levels (more than 100,000 cells/mm³), mechanical obliteration of small pulmonary blood vessels by tumor cells occurs, which impairs gas exchange.
What else to study on this topic
- Hematogenous pulmonary metastases: main primary sources and CT semiotics of nodules
- Lymphangitic carcinomatosis: differential diagnosis with interstitial edema
- Post-radiation pneumonitis: how to distinguish therapy complications from lymphoma relapse
- Opportunistic pulmonary infections in immunocompromised oncohematology patients
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