Purpose or Case Report: Ultrasound is a valuable tool for evaluating lymph nodes in the context of an inflammatory response. Lymph nodes are crucial in the body's immune system, and changes in their size, shape, and echogenicity can provide valuable information about the underlying pathology. What is expected in the inflammatory response is the maintenance of its typical characteristics such as dimension, fatty hilum, thin cortex and hilar flow, however, some pathologies may present atypical lymph node enlargement. These findings are not considered pathognomonic manifestations but they can give us very important tips to direct us to the correct diagnosis as we describe in our case series: 1. Cat-scratch disease: male patient, 10-year-old, with painful epitrochlear, cervical and axillary lymph nodes for 3 months. Ultrasound (US) showed enlarged hypoechogenic lymph nodes (local lymph nodes in the same region as the cat scratch). Serological test confirmed cat scratch disease diagnosis. 2. Bacille Calmette–Guérin lymphadenitis: male patient, 7-months-old, with post vaccination right axillary lymphadenopathy. US revealed right enlarged axillary lymph node, hypoechogenic, containing tiny hyperechoic foci. 3. Lymphomatous lymph nodes: male patient, 17 years old, with painless cervical node for 4 months. US showed enlarged, heterogeneous lymph node, with loss of fatty hilum and well-defined walls, with typical findings by color Doppler study, as we will show. Immunophenotyping: non-Hodgkin's lymphoma. 4. Streptococcus Lymphadenitis: 6-year-old female patient with cervical lymph nodes. US showed Streptococcus lymphadenitis common findings: enlarged hypoechoic lymph nodes, oval-shaped, with thick capsule and hyperechogenicity of adjacent tissue. Increased central and peripheral blood flow by color Doppler. Swab test confirmed Streptococcus. 5. Thyroid tumor metastasis: 17-year-old male patient with a palpable cervical nodule. US showed a solid hypoechoic thyroid nodule and local lymph node with calcifications. Biopsy confirmed papillary thyroid carcinoma with secondary involvement of lymph node. Learning points: 1. Anatomical review of the cervical lymph node chains by ultrasound. 2. Learn typical sonographic features of atypical lymph nodes; 3. Value the importance of correlation of imaging findings with clinical data, tests and biopsy; 4. Assess the pediatric cases from our pediatric radiology group that will be useful for your future atypical cases.
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