Stansfeld distinguishes predominantly inflammatory reactions, caused mainly by bacteria and fungi, and predominantly immune reactions, which are more often the effects of viruses or drugs. The reactions of lymph nodes to foreign substances are diverse and difficult to separate into specific patterns. Some of these are amorphous foreign bodies, which are simply phagocytized and degraded others are antigenic and therefore able to trigger an immune reaction. Thus, a large variety of substances are carried to the lymph nodes. To recall the main etiologic categories, some authors suggest using acronyms like MIAMI ( malignancies, infections, autoimmune, miscellaneous, and iatrogenic) ( 3).Īn essential function of lymph nodes is to filter the lymph drained from their tributary regions. For the etiologic investigation of lymphadenopathies, various algorithms have been proposed, including successive branches in which the various entities are ruled out depending on the response to laboratory tests, medications, and follow-up ( 1). Notwithstanding, in the search for specific etiologic agents in the investigation of lymphadenopathies, the prevailing objective in the majority of cases is to determine the presence or absence of a neoplastic process. Most enlarged lymph nodes involved by RLH or atypical lymphoid hyperplasia do not exhibit morphologic patterns indicative of specific agents, and therefore the cause of RLH is listed as unknown. Still, the cases of RLH in which an etiologic agent is identified represent only a fraction, probably fewer than 10%, of all hyperplastic lymph nodes.

In others, characteristic morphologic patterns may suggest an etiologic diagnosis without proving it directly such a situation must be clearly indicated in the final diagnosis. In some cases, specific microorganisms can be detected on regular sections and identified by special stains, in situ hybridization, polymerase chain reaction (PCR), or other procedures, so that an etiologic diagnosis is possible. Additional epidemiologic data to be considered in the diagnosis of lymphadenopathies are environmental factors such as tobacco smoking, occupational exposure to silicon, beryllium or other pneumoconioses, close contact with animals particularly cats, travel to places of endemic infections (see Lymphadenitides), and high-risk sexual behaviors. In a study of 628 lymph node biopsies, 79% were benign lymphadenopathies in patients younger than 30 years of age, 59% in those between 30 and 50 years, and 39% in patients older than 50 years ( 5). In children, most lymphadenopathies are benign, whereas in adults, the probability of malignancy (metastatic carcinoma more so than lymphoma) increases with age ( 4).

The age of patients is one of the most important factors in determining the nature of enlarged lymph nodes. In family practice or general medical practice, malignancies represent only about 1.1% of lymph node lesions, whereas at referral centers their frequency is 40% to 60% ( 1, 2, 3). The ratio of non-neoplastic to neoplastic lymph node lesions varies greatly with the kind of medical practice in which they present. Nevertheless, the challenge is to detect those lymph nodes affected by neoplastic processes in order to apply timely and efficient therapeutic measures. The vast majority of enlarged lymph nodes are non-neoplastic. They represent the reaction of lymphoid tissues to some of the immense variety of intrinsic and environmental antigens. Lymphadenopathies, manifested clinically by the enlargement of lymph nodes, are a common occurrence.

Shotty lymph nodes children