Lymphadenopathy refers to the enlargement of lymph nodes due to various causes, such as infections, inflammation, or malignancy. It can be localized (involving a specific group of nodes) or generalized (involving multiple groups).
Etymology:
“Lymph” is derived from the Latin “lympha,” meaning clear water, referring to the lymph fluid circulating through the lymphatic system. “Adenopathy” comes from the Greek “adenos” (gland) and “pathos” (suffering), meaning a disease of the glands, referring to the lymph nodes in this context.
How does it appear on each relevant imaging modality:
Chest X-ray:
Parts: Lymphadenopathy may be seen as enlarged lymph nodes, particularly in the hilar or mediastinal regions.
Size: Enlarged lymph nodes are often visible on lateral views when they exceed a certain size, usually greater than 1 cm in the mediastinum.
Shape: Nodes can appear round, oval, or irregular in shape.
Position: Typically found in the hilum or mediastinum; cervical or supraclavicular lymphadenopathy may also be visible.
Character:
Sometimes larger calcifications can be seen on a CXR
CT Scan:
Parts: Lymph nodes appear as rounded or oval soft tissue masses,
Size: Enlarged nodes are usually defined as being greater than 1 cm in diameter in the short axis. Nodes greater than 1 cm are more likely to be pathological,
Some reports suggest that the subcarinal node should be greater than 1.2cms to be considered pathological
Shape:
Most are usual round oval
Position:
Can be visualized in the mediastinum, hilar, or cervical regions.
Character:Pathological
Homogeneous soft tissue density
Calcification: Lymph nodes can exhibit calcification, which is important in determining etiology:
Central calcification:
Often seen in benign conditions such as tuberculosis or histoplasmosis.
Eggshell calcification: A distinctive finding in
sarcoidosis
silicosis
Psammomatous calcification:
malignancy.
papillary thyroid cancer
mucin secreting metastases
sarcoidosis sometimes early calcification is “sand-like”
Pathological vs Non-pathological distinction:
Pathological lymphadenopathy is typically characterized by nodes greater than 1 cm in size,
Non-pathological lymphadenopathy,
normal in size or
enlarged
MRI:
Not usually used for evaluation of lymph nodes
PET-CT:
Role:
PET-CT is
crucial for assessing the
metabolic activity of enlarged lymph nodes, particularly for malignancy.
It helps distinguish between pathological and non-pathological nodes by detecting increased glucose metabolism,
typically seen in malignant nodes
or active inflammatory conditions or infections.
The size of the node usually has to be larger than 7mm but if there is a significant hypermetabolic level it will show activity even if smaller than 7mm
