Pyothorax-associated lymphoma (PAL) is a non-Hodgkin lymphoma of exclusively B-cell phenotype that develops in the pleural cavity of patients after a long-standing pyothorax or empyema.
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Epidemiology
Associations
There is a strong association with EBV infection.
Pathology
Location
Commonly reported locations include 3:
- lateral costal pleura ~50%
- costophrenic angle ~30%
Microscopic appearance
Histologically, pyothorax-associated lymphoma usually shows a diffuse proliferation of large B-cells (diffuse large B-cell lymphoma (DLBCL)).
Radiographic features
CT
May be seen as a lenticular or crescent-shaped soft tissue mass straddling the thickened pleura at the margin of a coexistent empyema cavity 3. It has a tendency to invade adjacent structures. Air-fluid levels or gas within the empyema cavity may also be present.
Treatment and prognosis
It is responsive to chemotherapy, but the overall prognosis is considered poor 1.
Differential diagnosis
In some situations, differential considerations include:
- empyema necessitans
- other pleural malignancies:
- chest wall based malignancy invading into pleura
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