3.1. TB Lymphadenitis

Lymph node TB is one of the most common forms of EPTB, and cervical lymph nodes are the most common site with or without associated disease of other lymphoid tissue. It usually occurs in the age group of 5-9 years. The presenting features are enlarging masses over weeks to months. Cervical lymph nodes, particularly jugular, posterior triangle and supraclavicular, are affected; axillary and inguinal are sometimes involved. Systemic symptoms may be seen in some patients. A clinical correlate of diagnosis includes progressive enlargement of lymph node for more than two weeks, firm, minimally tender or non-tender, with or without fluctuation. Affected nodes may get matted, turn into a cold abscess and may rupture and develop chronic sinus. Moreover, large lymph nodes may be present due to various infections or malignancy. Histopathology is the usual gold standard test for establishing the aetiology of enlarged nodes. Fine Needle Aspiration Cytology (FNAC) is an alternative test usually considered adequate for accurate diagnosis as it correlates well with biopsy in more than 90% of cases.  However, both these tests require a skilled pathologist to report on the specimen and therefore, these tests are may not always be feasible in the peripheries. Besides, needle aspirate from the node can be easily tested for the presence of AFB or NAAT to diagnose TB in such cases in a more decentralised fashion without needing the services of a skilled pathologist. However, since there are better alternatives available and the yield of smear for AFB / NAAT is moderate at best, all cases negative for these tests should be subjected to a detailed FNAC/ histopathology.  In the case of tuberculosis, histopathology typically shows epithelioid granuloma with or without central acellular necrosis (Annexure 4 for Needle aspiration of LN and similar swellings video available at: https://tbcindia.gov.in/index1.php?lang=1&level=3&sublinkid=5320&lid=3419 )

 

 

 

Figure. 3 Diagnostic Algorithm for Tubercular Lymphadenitis

 

Ultrasonography may be helpful to identify affected non-palpable or deep-seated nodes for needle aspiration and testing. Central hypoechogenicity in a node on USG is considered suggestive of TB and may improve testing yield by targeting such nodes for aspiration. 

Furthermore, on chest X-Ray, 5-40% of patients identified to have peripheral TB lymphadenitis may have pulmonary/ pleural abnormalities, hilar/ mediastinal lymph nodes, parenchymal lesions or pleural effusion. Skin test for TB test is positive in a significant proportion (>70%) of patients but does not contribute to establishing the diagnosis. Reactive adenitis in a child with positive TST does not mean TB adenitis.

In children, lymphadenopathy is expected due to recurrent tonsillitis and upper respiratory tract infections. Reactive lymphadenitis may clinically mimic tuberculosis but do not warrant anti-TB drugs. Hence, anti-TB drugs should not be given unless the diagnosis of TB is confirmed by microbiological tests (smear for AFB or NAAT / Mycobacteria Growth Indicator Tube (MGIT) for M.tb ) or by suggestive FNAC or histopathology. Figure 3, depicts the diagnostic algorithm for tubercular lymphadenitis.