Retrograde spread of metastasis to hilar and mediastinal
nodes from cancer kidney.
The incidence of lymph node metastasis is high with extra thoracic
primaries, as
well as bronchogenic carcinoma.
Autopsy incidence related to various primaries range from
20-60%.
However, the reported incidence and radio graphically visible lymphadenopathy vary
greatly.
Radio graphically visible enlargement is probably found in less than 5% of all
patients with extra thoracic primary neoplasms.
Head and neck and genitourinary tract
neoplasms most often cause visible intrathoracic enlargement followed by malignant
melanoma and breast carcinoma.
Diagnostic challenge
Lymphadenopathy may be hilar, mediastinal or both.
This opposed to sarcoidosis,
which rarely causes mediastinal nodular enlargement without hilar enlargement.
Lymph node metastasis is not always associated with lung metastasis.
The
radiographic appearance may, therefore, be indistinguishable from sarcoid, non-infectious
granulomatous disease, lymphoma, leukemia or a primary mediastinal tumor.
Diagnostic
problems arise in the minority of patients who do not have known primary neoplasms.
Asymptomatic patients with symmetric hilar enlargement usually have sarcoidosis.
Metastatic disease may cause bilateral hilar enlargement. However, these patients are
usually symptomatic.
Anterior mediastinal node masses are common in lymphoma but rare in
sarcoid, as seen on chest radiographs.
