Does a Normal Lymph Node Have a Blood Flow Signal?

Lymph nodes, the fundamental components of the lymphatic system, are oval or broad-bean shaped, varying in size, and distributed throughout the body. They somewhat resemble masses or tumors. When diagnosing the nature of masses or tumors, blood flow signals are often utilized for testing. The intensity of these blood flow signals is associated with the benignity or malignancy of the mass, as well as its size. Consequently, some individuals may be concerned about the presence of blood flow signals in normal lymph nodes.

1. Do Normal Lymph Nodes Have Blood Flow Signals?

Surrounding normal lymph nodes, there are no blood flow signals. If blood flow signals are detected around lymph nodes during ultrasonic examination, it suggests the presence of tumor-metastasized lymph nodes. Normal lymph nodes are surrounded by lymphatic vessels, including afferent and efferent lymphatic vessels, and they have a distinct lymph node hilum. However, there are no blood flow signals surrounding them. In cases of tumor metastasis, the morphology of the lymph nodes may change to a rounded shape, with the disappearance of the lymph node hilum. Abnormal blood flow signals may be present in the surrounding area, necessitating careful search for the primary tumor site. If the primary tumor site can be identified, radical surgical resection is indicated. If the primary tumor site cannot be located, surgical removal of enlarged lymph nodes and subsequent pathological examination may be necessary.

2. What Are Blood Flow Signals?

Blood flow signals refer to the degree of blood flow richness, which is typically classified into four grades: Grade 0 indicates no blood flow signals within the mass; Grade 1 indicates minimal blood flow with 1-2 punctate blood flow signals within the mass; Grade 2 indicates moderate blood flow with 3-4 punctate blood flow signals or one clearly visible vessel wall within the mass; and Grade 3 indicates rich blood flow with more than 4 punctate blood flow signals or two clearly visible vessel walls within the mass. Generally, malignant masses tend to have richer blood supply than benign masses, with the former often exhibiting Grade 2-3 blood flow and the latter typically Grade 0-1 blood flow. Among tumors, 86.96% of malignant cases show Grade 2-3 blood flow, while 91.3% of benign cases show Grade 0-1 blood flow. Although the degree of blood flow richness is associated with the benignity or malignancy of masses, it also correlates with their size. Some larger benign breast masses may exhibit rich blood flow signals, while small breast cancers may not show any blood flow signals due to their small size, relatively few and thin neovascularizations, and limitations in instrument sensitivity that may hinder the detection of low-speed blood flow in small vessels.

CDFI (Color Doppler Flow Imaging) is used to visualize blood flow in the human body, while two- and three-dimensional ultrasound imaging techniques reveal anatomical structures. Together, these technologies provide comprehensive anatomical information. Based on CDFI, which does not require directional separation or frequency demodulation, the detection threshold can be lowered to facilitate the visualization of low-speed blood flow in small vessels. However, CDFI cannot distinguish between blood flow direction and velocity.