Lymph nodes are small, bean-shaped structures that are part of the body’s immune system. They filter harmful substances and house immune cells that fight off infections and diseases. When imaging tests reveal “cortical thickening” of a lymph node, understanding its significance is important.
Understanding Lymph Nodes and Cortical Thickening
Lymph nodes are small, oval or kidney-shaped glands that filter lymph, a clear fluid containing white blood cells, proteins, and waste products from body tissues. They are located throughout the body, acting as checkpoints where immune cells identify and eliminate foreign invaders like bacteria and viruses, as well as damaged or abnormal cells, including cancer cells. Each lymph node is enclosed by a capsule and divided into regions. The outermost layer is known as the cortex, where much of the immune cell activity occurs. This region is rich in lymphocytes, which are important for an immune response.
Cortical thickening refers to an enlargement of this outer layer of the lymph node. This structural change typically results from an increase in the number of immune cells within the cortex. It is an observation made during imaging, rather than a diagnosis itself. The thickening indicates that the lymph node is actively involved in an immune process, which can have various causes.
When Cortical Thickening is a Normal Finding
Cortical thickening is frequently a normal and expected physiological response, reflecting the lymph node’s role as an active immune factory. When the body encounters an infection or inflammation, the immune cells within the lymph node cortex proliferate to fight off pathogens. Common, benign reasons for this thickening include recent or ongoing infections like a common cold, strep throat, ear infections, or dental issues. Localized inflammation from an injury or irritation in the area drained by the lymph node can also cause this response.
Even routine medical interventions like vaccinations can lead to temporary cortical thickening. For instance, mRNA COVID-19 vaccines have caused increased cortical thickening and vascularity in armpit lymph nodes on the injection side. This reactive thickening can persist for weeks or months, gradually diminishing over time.
When Cortical Thickening May Indicate Concern
While often a benign finding, cortical thickening can sometimes indicate an underlying issue. Certain characteristics observed during imaging or physical examination may raise concern. These include lymph nodes that are persistently enlarged, rapidly growing, or feel abnormally firm or fixed to surrounding tissues.
The presence of other symptoms alongside cortical thickening can also be important. These may include unexplained weight loss, night sweats, fever, or persistent fatigue. On imaging, features such as a lymph node losing its typical oval shape and becoming more rounded, or the absence of its central fatty hilum, can be concerning.
While a cortical thickness greater than 3 millimeters can be considered suspicious, especially if it’s focal or asymmetric, a thickness exceeding 6 millimeters is often considered more concerning. Unilateral lymphadenopathy, where only one side of the body is affected, may also increase suspicion. Though less common, conditions such as certain autoimmune diseases like lupus or rheumatoid arthritis, or malignancies like lymphoma or metastatic cancer, can also manifest with cortical thickening.
Diagnostic Approaches and Follow-Up
When cortical thickening of a lymph node is noted, a healthcare professional typically begins with a thorough review of the patient’s medical history and a physical examination. This initial assessment helps in understanding potential causes and guiding subsequent steps. Depending on the findings, further imaging studies may be recommended, such as additional ultrasounds, CT scans, or MRI scans, for a more detailed view. Sometimes, blood tests might also be ordered to check for infection or inflammation.
If the cause of cortical thickening remains unclear or suggests a more serious condition, a biopsy may be performed. A biopsy involves removing a tissue sample from the lymph node for microscopic examination. This procedure can help differentiate between benign conditions, infections, and malignancies. Types of biopsies range from fine-needle aspiration, which collects cells, to core needle or open surgical biopsies, which obtain larger tissue samples. A biopsy is not always necessary; only a medical professional can provide an accurate diagnosis and appropriate guidance.