Lymph Node Disorders Workup

• In most patients, only the history and physical examination are needed to establish the likely diagnosis. However, if the diagnosis needs to be further refined, several tests can be performed. Generally, clinicians should perform the least invasive test that provides the most information. Furthermore, clinicians should tailor tests to the most likely diagnosis instead of performing a battery of tests on all patients with lymphadenopathy. Tests may include laboratory or radiologic investigations.
• Various laboratory tests are available. In general, most laboratory indices of inflammation (eg, erythrocyte sedimentation rate, C-reactive protein, glycoproteins, fibrogen levels) do not contribute much to establishing the diagnosis because most of the results are invariably elevated and do not provide a suggestion regarding the exact etiology of the lymphadenopathy. Tests that are more specific are much more likely to help the clinician with the treatment of the patient.
• A CBC count with a manual differentiation provides useful information. Leukemias are often accompanied by pancytopenia. A predominantly lymphocytic elevation (>1 X 10⁹ cells/L) is practically diagnostic of mononucleosis; when the proportion of these cells is less elevated but still predominant, CMV and toxoplasmosis must be considered. Finding medium-to-large lymphocytes that can be classified as in transformation or activated is useful to indicate a viral infection.
• Other useful tests may be performed to confirm or exclude specific clinical suspicions. Serum lactate dehydrogenase (LDH) may be used to determine the turnover rate of cells in the case of leukemia or lymphoma. Other tests, such as tuberculin skin test; monospot; and titers for EBV, CMV, catscratch disease, or toxoplasmosis, may be performed to evaluate for specific etiologies.

• Chest radiography may be useful to assess for potential sources of infection, such as bacterial pneumonias or tuberculosis, and hilar adenopathy in the case of malignancy. Indeed, because numerous reports describe airway collapse with anesthetics in the case of a large anterior mediastinal mass, chest radiography should be considered before any general anesthetic is administered (see the image below). A preoperative radiograph showing a narrowed trachea secondary to an anterior mediastinal mass.
• Ultrasonography may be performed to distinguish the nature of the node if it is difficult to palpate. Furthermore, it may be used to distinguish the abnormality from other potential anatomic structures (eg, dermoid cysts, thyroglossal duct cysts, branchial cleft cysts, inguinal hernias, undescended testicles). Ultrasonography may reveal relationships to contiguous structures and offer information about the content of the enlarged lymph node or nodes (ie, solid, liquid, gas, homogeneous or nonhomogenous). Finally, in some current studies, ultrasonography has been used in an effort to establish etiology based on ultrasonographic characteristics.
• CT scanning is useful to depict deep lymph nodes, especially in the thoracic and abdominal cavities. This may be the only noninvasive technique available to evaluate these areas for other potential areas of lymphadenopathy and determine a potential source of malignancy (eg, neuroblastoma, Burkitt lymphoma, rhabdomyosarcoma). Furthermore, chest CT scanning may add to the information obtained from chest radiography and may depict an anterior mediastinal mass, as well as the extent of tracheal or bronchial airway compression (see the images below). A CT scan showing an anterior mediastinal mass and compression of the trachea. A CT scan showing an anterior mediastinal mass and compression of the left mainstem bronchus.
• 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) has been used in adult patients with lymphoma and, more recently, in children to assist in diagnosis and to monitor disease during therapy.^[7] Its use has been applied to both Hodgkin and non-Hodgkin lymphomas, with promising findings. However, clinicians must be cautious with use of 18F-FDG PET because a high number of false positive results in children have been reported due to higher inflammatory reaction to inciting agents.

• Fine-needle aspiration (FNA) biopsy has been used extensively in adults and is now being described in children.^{[8, 9, 10]} The cited advantages of FNA biopsy include the fact that it can be performed in the outpatient department, that it is simple and rapid, that it does not require a general anesthetic, that it has low morbidity, that it is cost effective, and that it produces minimal scarring.^[8]
• The sensitivity and specificity of FNA biopsy in determining the etiology of lymphadenopathy are more than 90%.^{[8, 10]} Most patients who have a benign diagnosis on FNA biopsy do not undergo surgical biopsy. However, in most centers, FNA is still not practiced in children. Furthermore, whether the advantages of FNA outweigh the perceived limits has not been established. These limits include center dependence on pathologists who are accustomed to making diagnoses on FNA alone, the potential risk of seeding a tract with malignancy, and the continued need for at least conscious sedation in most children. Most oncology protocols now require special studies to be performed on the nodal tissue, including cytogenetics, flow cytometry, electron microscopy, and special stains that FNA does not allow.
• To obtain more tissue, some investigators have used core needle techniques with ultrasonography or CT guidance.^[11] This allows procurement of more tissue, which may be needed in difficult diagnoses.

Histologic findings vary depending on the etiology.

Staging is relevant only in malignant etiologies.