Cervical and intrathoracic lymph nodes
The distribution of affected lymph nodes varies significantly depending on the type of lymphoma.
Hodgkin Lymphoma (HL):
- Cervical lymphadenopathy is detected at presentation in the vast majority of patients (up to 80%). The tumor spreads predictably—to adjacent groups (contiguous), for example, from the internal jugular chain to deep lymphatic pathways.
- Intrathoracic nodes are frequently involved (60–85%). Prevascular and paratracheal groups (84%), as well as hilar nodes (hilar)—28%, are predominantly affected. Involvement almost always encompasses ≥2 groups. Isolated enlargement of a hilar node without mediastinal involvement is atypical.
- Nodular sclerosis almost always involves the anterior mediastinum.
Non-Hodgkin Lymphoma (NHL):
- In the neck, it is frequently associated with involvement of Waldeyer's lymphatic ring (Waldeyer’s ring), which is considered equivalent to a lymph node during staging.
- Spread often has an intermittent, non-contiguous (non-contiguous) character.
- Intrathoracic nodes are involved less frequently (25–40%), with up to half of cases limited to the involvement of a single anatomical group only.
Abdomen, retroperitoneum, and pelvis
To evaluate nodes below the diaphragm, the localization of enlarged masses is essential:
- Retroperitoneal nodes: involved more frequently in NHL (up to 55%) than in HL (25–35%).
- Mesenteric nodes: mesenteric involvement is a hallmark marker of NHL (occurring in more than 50% of cases), whereas it is rare in HL (less than 5%). Lymphoma is a known cause of the CT "misty mesentery" sign (misty mesentery).
- Organ hila: splenic hilar nodes are involved in approximately 30% of patients and are almost always combined with diffuse infiltration of the spleen itself. The porta hepatis (porta hepatis) is also more commonly involved in NHL.
- Pelvis: any group may be involved. Enlargement of inguinal and femoral nodes in HL is rare (less than 20%). MRI is preferred for accurate evaluation of massive pelvic disease (massive pelvic disease).
CT semiotics and imaging patterns
Affected nodes in lymphoproliferative disorders have a characteristic contrast enhancement pattern—they accumulate the agent uniformly. Multilocular (multilocular) enhancement or the presence of central necrosis is atypical for lymphomas; such findings require the exclusion of tuberculosis, atypical infections, or squamous cell carcinoma metastases.
In the abdominal cavity, nodal masses in NHL tend to form large conglomerates (bulky disease). If such masses compress a bowel loop (often the horizontal part of the duodenum), the hamburger sign (hamburger sign) is formed on axial CT slices.
An important diagnostic challenge in HL is that spread follows direct lymphatic pathways (e.g., via retrocrural nodes to the celiac trunk), but the nodes themselves may be normal in size or only minimally enlarged (>6 mm) while already being infiltrated by the tumor.
Extranodal involvement and choice of method (CT or PET/CT)
Extranodal involvement is significantly more common in NHL. Primary extranodal disease occurs in 35% of NHL cases (only regional nodes are involved, stages IE–IIE). This variant is extremely rare in HL. T-cell lymphoblastic lymphomas, mantle cell lymphoma, Burkitt lymphoma, and MALT lymphomas have a predisposition for extranodal growth.
FDG PET/CT outperforms conventional CT in detecting bone marrow, splenic, and normal-sized node infiltration. This results in upstaging (upstaging) in 40% of patients (e.g., changing from stage II to stage IV upon the detection of spinal lesions). However, unenhanced and contrast-enhanced CT remain critical as they can visualize small pulmonary nodules in low-grade lymphomas (low-grade), the sizes of which fall below the PET resolution threshold.
Briefly: answers to topical questions
Which anatomical zones of the neck and pharynx are involved in non-Hodgkin lymphomas?
In non-Hodgkin lymphomas, non-contiguous groups of lymph nodes are affected in the neck, and the process in the pharynx frequently involves the lymphoid tissue of Waldeyer's ring.
This structure includes the following zones:
- Adenoids—located in the nasopharynx.
- Palatine tonsils (faucial tonsils)—located laterally in the oropharynx.
- Lingual tonsil (lingual tonsils)—located at the anterior base of the tongue.
Cervical adenopathy in this condition is less common than in Hodgkin lymphoma, and the affected node groups are more frequently non-contiguous (non-contiguous).
What are the diagnostic criteria for massive mediastinal involvement in Hodgkin lymphoma?
The diagnostic criteria for massive mediastinal involvement in Hodgkin lymphoma are specific size parameters of the tumor conglomerate on computed tomography.
Criteria for bulky disease (bulky):
- Isolated mass—the maximum diameter of the lesion exceeds 10 cm.
- Chest ratio—the size of the lesion accounts for more than 1/3 of the thoracic transverse diameter on CT.
Morphologically, such large anterior mediastinal masses typically represent thymic infiltration combined with a lymph node conglomerate (nodal mass). Such involvement is recognized as an unfavorable prognostic factor.
To remember the pattern of spread: Hodgkin "walks" sequentially (contiguously along chains, often in the neck and mediastinum), whereas Non-Hodgkin lymphomas "jump" (non-contiguously, affecting the mesentery and Waldeyer's ring).
Class and exam questions
How to differentiate an enlarged lymph node in lymphoma from squamous cell carcinoma metastasis on CT?
In lymphomas, lymph nodes typically enhance evenly and homogeneously. The presence of central necrosis (multilocular enhancement) is atypical for lymphomas and rather points to metastasis or tuberculosis.
What is the "hamburger sign"?
This is a CT sign that occurs with massive involvement of mesenteric or retroperitoneal lymph nodes (often in NHL). Tumor masses compress the bowel loop from both sides, which resembles layers of a hamburger on an axial slice.
What is the main advantage of PET/CT over contrast-enhanced CT in staging?
PET/CT has high sensitivity for hypermetabolic lesions, making it possible to detect bone marrow, splenic, and normal-sized lymph node involvement. This leads to disease upstaging (upstaging) in approximately 40% of cases.
What else to study on this topic
- Features of NHL staging with involvement of Waldeyer's lymphatic ring.
- CT presentation of primary mediastinal large B-cell lymphoma with pleural and pericardial involvement.
- Algorithm for locating the omental bursa (Winslow foramen) lymph node on CT scans.
- Transformation of follicular lymphoma to DLBCL: radiological signs of grade escalation.
- Differential diagnosis of the causes of the CT "misty mesentery" sign.
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