Lymphadenitis in the pediatric population frequently is benign and self-limited, often caused by infections. In children with refractory symptoms, lymph node biopsy may be indicated to rule out malignancy or obtain material for culture. Acute bacterial infections typically show a suppurative pattern of necrosis with abscess formation. Viral infections are associated with nonspecific follicular and/or paracortical hyperplasia. Granulomatous inflammation is associated with bacterial, mycobacterial, and fungal infections. Toxoplasma lymphadenitis displays follicular hyperplasia, monocytoid B-cell hyperplasia, and clusters of epithelioid histiocytes. Autoimmune and noninfectious inflammatory disorders are included in differential diagnosis of lymphadenitis. Infectious mononucleosis and Kikuchi-Fujimoto lymphadenitis may mimic Hodgkin and non-Hodgkin lymphomas.
Infections are the leading cause of lymphadenitis in children.
The histopathologic patterns may suggest a specific etiology in some cases of pediatric lymphadenitis; however, confirmation requires correlation with clinical findings and results of other laboratory testing.
A pattern of immunoblastic paracortical hyperplasia is associated with viral infections, such as infectious mononucleosis and immunodeficiency-associated lymphoproliferative disorders.
Granulomatous inflammation in cervical lymph nodes of young children frequently is caused by atypical mycobacterial infections.
Some features seen in infectious or reactive disorders may mimic those seen in Hodgkin and non-Hodgkin lymphomas.
Peripheral lymphadenopathy leading to palpable lymph nodes is a frequent finding in the pediatric population. , In infants, occipital and postauricular lymph nodes are more commonly palpable, whereas in children over 2 years of age, cervical and sometimes inguinal lymph nodes are affected more frequently. In at least 75% of cases, peripheral lymphadenopathy is benign, self-limited, and managed conservatively. , A more comprehensive diagnostic investigation, including blood testing, serology, and imaging studies, may be required in refractory or symptomatic cases. Clinical studies of pediatric cervical lymphadenopathy reveal no identifiable etiology in as many as 67% of cases. Infections represent the most common identifiable cause, in particular viral upper respiratory infections and Epstein-Barr virus (EBV). , Autoimmune or inflammatory diseases, such as systemic lupus erythematous (SLE), Kikuchi-Fujimoto lymphadenitis, Castleman disease, and sarcoidosis, are uncommon, representing fewer than 1% of cases of pediatric lymphadenopathy worldwide.
A tissue biopsy typically is recommended when there is clinical or parental concern for malignancy. In samples negative for malignancy, histopathologic examination seldom reveals the specific etiology of the lymphadenitis. In cases of positive identification using microbiologic studies, bacteria and nontuberculous mycobacteria are reported most frequently.
In this article, the histopathologic patterns associated with pediatric lymphadenitis are reviewed. Patterns that mimic malignancies are discussed. Recognizing the etiology associated most frequently with each of these patterns may be helpful in narrowing down a clinical differential diagnosis and guide additional testing.