Submandibular Lymph Nodes

Submandibular lymph nodes are sometimes referred to in radiology reports when they are abnormal.  Submandibular nodes are located beneath the lower jaw (mandible) and play an important role in the immune system.   This article discusses the causes of abnormal submandibular lymph nodes and the imaging tests used for diagnosis.

What Are Submandibular Lymph Nodes?

The submandibular lymph nodes are part of the cervical lymph node chain, positioned in the submandibular triangle of the neck. These nodes typically range in size from 0.5 cm to 1.5 cm and are often seen on imaging when a patient presents with symptoms such as swelling, pain, or masses in the head and neck region.

Imaging of the submandibular lymph nodes is usually performed using:

•Ultrasound (US): The first-line imaging modality due to its wide availability and ability to differentiate solid from cystic structures.

•Computed Tomography (CT): Provides detailed evaluation, often used in cases of suspected malignancy or deep infections.

•Magnetic Resonance Imaging (MRI): Ideal for soft-tissue contrast, frequently used in cancer staging or complex infections.

Why Submandibular Lymph Nodes Appear on Imaging

Submandibular lymph nodes may show up on imaging for various reasons, including:

1.Infections: Conditions such as pharyngitis, tonsillitis, or dental infections can cause the nodes to swell, a condition known as lymphadenopathy.

2.Cancer Screening or Staging: Enlarged or irregular lymph nodes may indicate malignancies like lymphoma, head and neck cancers, or metastatic spread from other regions.

3.Inflammatory Disorders: Autoimmune diseases such as lupus or sarcoidosis can lead to lymph node enlargement.

4.Unknown Masses: A persistent lump in the submandibular area often prompts imaging to determine its cause.

Abnormal Findings to Note

1.Enlarged Nodes or asymmetric enlargement.

2.Loss of Hilum: Absence of the fatty hilum on ultrasound is concerning and can indicate malignancy.

3.Irregular Margins: Nodes with blurred edges or spiculations suggest infiltration, commonly seen in metastatic disease.

4.Necrosis or Cystic Changes: Central necrosis, visible as low-density areas on CT or a non-enhancing core on MRI, often indicates abscess formation or cancer.

5.Calcifications: Tiny calcifications within a node, particularly on CT, may point to previous infections like tuberculosis or metastatic thyroid cancer.

When Is Imaging Recommended for Submandibular Lymph Nodes?

1.Persistent Swelling or Pain: If submandibular swelling does not improve, imaging can help identify the underlying cause.

2.Systemic Symptoms: When paired with unexplained weight loss, fever, or night sweats, imaging may help diagnose serious conditions like lymphoma or metastatic disease.

3.Unexplained Lump: Any firm, immobile mass in the submandibular area should be evaluated with imaging.

Ultrasound: A First-Line Tool for Submandibular Nodes

Ultrasound is the preferred initial modality for evaluating submandibular lymph nodes due to its real-time imaging and lack of radiation. Key features radiologists look for include:

•Shape and Size: Normal nodes are typically oval. A round shape may indicate pathology.

•Vascularity: Color Doppler can detect increased blood flow, often seen in inflamed or malignant nodes.

•Texture: Cystic or heterogeneous textures may require further workup.

Personal Insight: In my practice, I’ve noticed that enlarged but well-defined submandibular lymph nodes with preserved hilum on ultrasound are often reactive, resolving with treatment for infections.

CT and MRI for Detailed Assessment

When ultrasound findings are inconclusive, or deeper evaluation is necessary, CT and MRI are the next steps.

Radiologists use CT and MRI for cancer staging, as these modalities help identify lymph node involvement.

Imaging in Submandibular Lymphadenopathy

Submandibular lymphadenopathy (swollen nodes) is a common condition seen on imaging. The cause can range from benign to life-threatening:

•Reactive Lymphadenopathy: Enlarged nodes due to infections or inflammation. They typically shrink after the infection resolves.

•Neoplastic Lymphadenopathy: Suspicious nodes with irregular shape, loss of hilum, and necrosis require biopsy for diagnosis.

•Chronic Lymphadenopathy: Tuberculosis and sarcoidosis often present with persistently enlarged nodes with calcifications.

Submandibular Lymph Nodes in Cancer Staging

One of the most important roles of imaging is in cancer staging. Head and neck cancers, thyroid cancers, and lymphoma can involve the submandibular nodes. Radiologists assess the following:

•Size and shape of nodes.

•Distribution of involved nodes (single vs. multiple).

•Appearance of nodes

Imaging findings often guide biopsy decisions and treatment planning.

Tips for Patients Undergoing Imaging

If your radiology report mentions submandibular lymph nodes, it’s essential to:

1.Ask Questions: Speak with your doctor about the findings and what they might mean.

2.Follow Recommendations: Your healthcare team may suggest further imaging, blood tests, or a biopsy if the nodes appear abnormal.

3.Stay Informed: Understanding the imaging process helps reduce anxiety and ensures proper follow-up care.

Conclusion

Imaging of submandibular lymph nodes provides information about a wide range of conditions, from simple infections to complex cancers. Early identification of abnormalities through modalities like ultrasound, CT, or MRI can lead to prompt and effective treatment.   Your doctor will combine the imaging information with your clinical history to determine the best path forward.

Reference Links:

1.https://www.ajronline.org/doi/10.2214/ajr.184.5.01841691

2.https://insightsimaging.springeropen.com/articles/10.1007/s13244-018-0615-4

3.https://www.ajronline.org/doi/10.2214/ajr.174.3.1740837