This report describes the case of a 76-year-old woman diagnosed with Epstein-Barr virus-positive diffuse large B-cell non-Hodgkin lymphoma of the elderly. She had an unusual presentation of the disease with widespread skeletal muscle, masticatory muscle, and parotid gland involvement and the development of interesting erythematous lesions in the neck during chemotherapy. One month after completion of chemotherapy, positron-emission tomography (PET) showed features of persistent lymphoma, but a repeat PET scan a month later showed no active disease. This case reiterates 2 important points: first, to consider lymphoma a differential diagnosis in masticatory muscle enlargement and second, to question false positivity when interpreting post-treatment PET scan results, especially in the absence of clinical disease.