Solid gastrointestinal tumors. Ultrasound cannot differentiate reliably between lymph nodes with metastatic invasion and those with benign lymphadenopathy. Frequently the lymph nodes are located within the drainage region of the tumor. Lymph node involvement has great prognostic significance in tumor staging (TNM system). When removing the tumor and the regional lymph nodes, the number of metastatic lymph nodes and their distance from the primary tumor are of additional prognostic importance (Fig. 6.9). In most cases, exact staging is possible only after pathological work-up since the mesenteric and parietal lymph nodes are superimposed on each other and thus defy precise demonstration. Endosonography is the imaging modality of choice when staging gastrointestinal tumors (except in the large and small intestines). In solid tumors the primary pattern of lymph node invasion is diffuse and micronodular as well as focal lymphadenopathy (micro and macro). “Bulky” formations are infrequent findings.

Malignant lymphoma. In the staging of malignant lymphoma, possible involvement of the abdominal lymph nodes carries with it far-reaching therapeutic consequences. If ultrasound cannot resolve the issue, additional CT studies are warranted. In patients with Hodgkin disease, staging laparotomy becomes necessary in only a few cases and is done only if the outcome has consequences for the treatment regimen. The sonographic image of abdominal lymph node involvement in malignant lymphoma covers a broad spectrum. Focal lymphadenopathy is most prevalent, with the lymphomas being well defined or confluent. Extremely “bulky” formations with concomitant displacement phenomena are not especially rare. If there is concurrent lymphoma, involvement of parenchymal organs of the gastrointestinal tract with an invasion pattern characteristic of lymphoma ultrasound will often be the first finding to raise the suspected diagnosis of malignant lymphoma.

In localized, primarily gastrointestinal lymphomas, any additional splanchnic (regional) lymph node involvement implies stage IIE1, while parietal (nonregional) in-

About 300 of the about 1000 lymph nodes in the human body are located in the cervical region. During childhood and adolescence, more than 80% of all enlarged lymph nodes are reactive in nature, depending on age. Posterocervical nuchal lymph nodes tend to be benign, whereas the lymph nodes of the supraclavicular fossa are often malignant.

Acute inflammatory lymphadenopathy ( 6.3c,d) has to be differentiated from chronic inflammatory (regressive) lymph node enlargement (Fig. 6.4). Usually, acutely inflamed lymph nodes are small (<1.5 cm), the hilar sign is present, and the length:width ratio (L/W) is greater than 2; they are not caked together and mostly display a homogeneous parenchyma (note: liquefying suppurating lymph node). Acute lymphadenitis is characterized by homogeneous hyperperfusion ( 6.3e,f), but lowlevel perfusion, or even lack of it, does not rule out reactive lymph node enlargement (Fig. 6.10). It has been suggested that horizon-

Fig. 6.10 A 13-year-old girl with fever and cervical lymphadenopathy.

a Enlarged homogeneous hypoechoic lymph node.

tal hilar vessels, longitudinal branches, and homogeneous vascular branching seen on colorflow Doppler scanning of the vascular supply of the lymph nodes are indicative of reactive lymphadenopathy ( 6.3i,j).

b Subcapsular vessels (1) and a focal lack of blood vessels

(2) on color-flow Doppler imaging. The initial findings raised a high suspicion of malignancy, while the followup indicated reactive lymphadenopathy.

In regressive lymph nodes, parenchymal calcification is possible ( 6.2j–l). On color-flow Doppler imaging, chronic inflammatory lymph nodes are characterized by a lack of flow.

Metastases

In metastasis, size is not a typical parameter and usually the hilar sign is missing (6.3 g,h). This type of lymph node tends to be round and hyperechoic ( 6.1a,b). Sometimes invasive growth can be demonstrated, necrosis is possible, and calcification of the parenchyma has also been observed ( 6.2n,o). The concentration of blood vessels varies on color-flow Doppler scanning. The vascular supply of the lymph

nodes has been said to indicate malignancy if color-flow Doppler imaging visualizes vascular displacement, aberrant vessels, and regions lacking any vascularization, and capsular vessels ( 6.3 m,n). Metastases exhibiting rapid growth have been shown to display a pathological vascularization with corkscrew-like vessels (Fig. 6.11). It is important to determine before surgery whether the metastatic cervical

lymph nodes can be delineated from the large blood vessels of the neck or whether there is vascular invasion. Contact between tumor and vessel wall over a distance of more than 3.5 cm, or over more than half the circumference, suggests vascular invasion (Fig. 6.12).

Fig. 6.11 A 72-year-old patient with malignant lymphoma and cervical lymph node metastasis.

a Hypoechoic lymph node.

b Corkscrew-like neovascularization. 1 = focal lack of vessels; 2 = aberrant vessels; 3 = subcapsular vessels.