Overview.
Pulmonary pseudolymphoma (PL), also known as nodular lymphoid tissue-like hyperplasia, is bronchial-associated lymphoid tissue originating from lymph nodes that are histologically distinct from true intrapulmonary lymph nodes. It is generally considered to be a benign lesion of inflammatory lymphocytic hyperplasia. The lesion usually appears as a single nodule and is confined to a single lobe of the lung.
Etiology
The etiology and pathogenesis of pulmonary pseudolymphoma are still unclear. Currently, it is thought that it may be related to an abnormal immune response and is an autoimmune disease. In addition, some studies have suggested that the use of the drug phenytoin sodium and viral infections are related.
Symptoms
A few patients have a previous history of pneumonia. Most patients have only mild cough and chest pain. It is usually detected on lung X-ray. The course of the disease is usually long and may remain unchanged for several years after diagnosis.
Examination
1. Laboratory tests
Some patients have abnormal immunoglobulinemia with elevated serum IgM, which is 7-8 times higher than normal.
2. Pathologic examination
Biopsy specimens are usually obtained during chest dissection and can be examined pathologically. Microscopically, there is obvious mixed cellular infiltration and varying degrees of fibrosis, and the histologic manifestations are different on different fields of view, but there is a clear tendency for central healing (scarring). Occasionally granulomas are seen.
3. Chest X-ray
It shows a single nodule or infiltration in the lungs as a limited solid lesion with clear margins and signs of bronchial insufflation, while enlargement of hilar and mediastinal lymph nodes is rare; the presence of enlarged lymph nodes tends to increase the likelihood of malignant changes in the disease. Pleural effusion is rarely seen on chest radiographs. Immunomarker assays show polyclonal type staining.
Diagnosis
The disease must be diagnosed on the basis of a biopsy specimen.
Differential Diagnosis
Pseudolymphoma is difficult to distinguish from low-grade malignant lymphoma, and the diagnosis must be confirmed by ancillary techniques such as immunophenotyping and gene rearrangement tests.
Treatment
Pseudolymphoma of the lungs is a benign condition but now tends to be considered a low-grade malignant tumor. Resection of the lesion with maximum preservation of normal lung tissue is the treatment of choice for pseudolymphoma. Although chemotherapy and radiation therapy are rarely required after resection, patients who have been surgically removed need to be followed closely to be alert for recurrence or the development of other lymphoproliferative disorders.
Prognosis
The disease is benign with satisfactory surgical results, but about half of the patients can develop malignant lymphoma. Both chemotherapy and radiation therapy can cause pulmonary pseudolymphoma to progress to malignant lymphoma.