In adults, under normal conditions, only the inguinal lymph nodes may be palpable as several, firm, 0.5- to 2-cm nodules attached to the dense fascia below the inguinal ligament. In children, small, 0.5- to 1-cm lymph nodes may be palpable in the cervical region. In both children and adults, palpable lymph nodes are commonly associated with various pathologic conditions. They may be isolated or part of a generalized lymphadenopathy, and they may occur without symptoms or during the course of systemic disease.

Most enlarged lymph nodes are nonneoplastic and represent their reaction to an infinite variety of antigens. In a general medical practice, neoplasia of lymph nodes is infrequent, about 1.1% of biopsies, whereas in referral centers their incidence may be as high as 60% (1,2,3).

In children, the criteria for performing the biopsy of an enlarged lymph node include the location, the age, the presence of lymph node fixation and tenderness. The biopsy is generally recommended for enlarged supraclavicular lymph nodes, children with prolonged fever, significant weight loss, and lymph node fixation to the overlying skin (4,5).

In children in the developing world, tuberculosis is a predominant cause of enlarged lymph nodes (33%), followed by nonHodgkin lymphoma (31%), as reported in the study of 242 children’s lymph node biopsies in Nigeria (6). In a study of 1877 cervical lymph node biopsies in children of South Africa, the mean age was 7 years and the vast majority showed nonspecific reactive lymphadenitis or granulomatous lesions of tuberculous origin (7).

Localized lymphadenopathies may involve lymph nodes in various anatomic sites. Some locations are more frequently associated with certain causative agents and are therefore considered to be suggestive of the cause of lymph node enlargement. Table 2.1 lists various causes of lymphadenopathy, with some of the locations most commonly affected.

The clinical and morphologic appearance of the enlarged lymph nodes depends on the causative agent, age of the patient, and status of host resistance. Biopsy specimens of enlarged lymph nodes are frequently obtained and, in 50% to 63% of cases, histologic examination leads to a positive diagnosis (8,9). The established diagnoses include specific lymphadenopathies (e.g., sarcoidosis; see Chapter 38), various lymphadenitides of known cause (e.g., infectious mono-nucleosis; see Chapter 9), metastatic tumors, and lymphomas (Fig. 2.1).

Magnetic resonance imaging helps localize cervicothoracic lesions in infants and children; the most frequently identified mass is lymphangioma (10). In adults, Doppler color flow ultrasonography images the intranodal vessel architecture (11). Cervical lymph node metastases can be separated from lymphadenitis based on peripheral perfusion or diffuse blood-flow patterns in metastases, but not by traditional ultrasonographic parameters such as size, homogeneity, shape, and brightness (12). Neck masses should be sampled if they are enlarging or unchanging, asymmetric, supraclavicular, or isolated, or if they are accompanied by fever or an enlarging liver, spleen, or Waldeyer ring (13). Contrast-enhanced computed tomography (CT) maps tuberculous and lymphomatous lymph nodes to somewhat different but frequently overlapping distributions. For example, disseminated and nondisseminated tuberculosis tends to involve lesser omental, mesenteric, anterior pararenal, and upper paraaortic lymph nodes; on the other hand, Hodgkin and non-Hodgkin lymphomas more often affect lower para-aortic lymph nodes (14). Lymph node enhancement on CT with a peripheral, multilocular appearance suggests tuberculous lymphadenopathy, whereas homogenous attenuation typifies lymphoma (14). Laparoscopically guided biopsy successfully confirmed a suspected diagnosis of abdominal lymphoma in 24 of 51 (47%) consecutive patients (15). Although technically difficult, laparoscopic biopsies can retrieve enough tissue to determine the exact stage of Hodgkin lymphoma involving liver, spleen, and lymph nodes (16).

In 37% to 53% of sampled lymph nodes, a definitive diagnosis is not reached (9,17,18). Most of the diagnoses in this group are various forms of nonspecific reactive lymphoid hyperplasia (see Chapters 32,33,34); only about 3% of all lymph node biopsies are classified as atypical lymphoid hyperplasia (19). In several studies, patients with nondiagnostic lymph node hyperplasia were followed from 2 to 20 years to ascertain the eventual outcome of their disease (8,9,18,19). Of 100 lymph node biopsies in children 9 months to 13 years old, 37 were classified as reactive hyperplasia, and 74% of these children were alive and well 20 years later (18). In two reviews of adults, about half of all lymph node biopsies remained without a specific diagnosis, and a disease related to the enlarged lymph nodes subsequently developed in 25% to 53% of the patients (9,19). In most cases, a definitive diagnosis became evident within 8 months to 1 year after the original biopsy, and
in 17% to 20% of cases, it was a form of lymphoma (9,19). When cases of atypical lymphoid hyperplasia were considered separately, the prevalence of lymphoma increased to 37% (19).