In children, a malignant lymphoma can present with life-threatening complications arising from progressive tumour growth, warranting swift diagnosis and treatment. Early recognition can be challenging if a child with paediatric lymphoma presents with abdominal and throat symptoms because of the frequency, and frequently benign nature, of these symptoms in the general paediatric population. In these cases, it is essential for the physician to recognize the alarm signals for suspicion of malignant lymphoma, to allow timely diagnosis and treatment. We present two cases (children age 8 and 16 years) demonstrating the symptoms of malignant lymphoma that should raise alarm in children presenting with unilateral tonsil enlargement or intussusception, and illustrating the importance of timely recognition of these alarm signals, to prevent life-threatening complications due to tumour progression. In patients presenting with unilateral tonsil enlargement, malignant lymphoma should be considered if atypical macroscopic tonsil morphology, cervical lymphadenopathy, dysphagia, snoring, fever or weight loss is present. The presence of a lead point as the cause of intussusception should be considered in children aged > 2 years of age, in a child with an ileo-iliac intussusception and in patients with longstanding abdominal symptoms. In patients presenting with simultaneous symptoms and alarm signals for malignant lymphoma, the relationship between the presenting symptoms should be recognized. Interdisciplinary and intradisciplinary consultation with colleagues can help in the search for an overarching diagnosis, and it is crucial that this should happen without delay to prevent acute life-threatening situations.