A 56-year-old female presented with clinical features of acute tonsillitis with subsequent cervical lymphadenitis. After taking empirical antibiotics for 1 week, the acute infection symptoms and signs were resolved. However, an asymmetric enlargement of the left palatine tonsil with ipsilateral neck swelling remained. Subsequent tonsillectomy and lymph node excisional biopsy were performed due to the possibility of malignancy. The patient was eventually diagnosed as malignant lymphoma according to pathological confirmation. We demonstrate the diagnostic challenges in such a rare case and emphasize the importance of differentiating malignant lymphoma from an atypically presenting acute infectious disease.