BACKGROUND Lymphomatoid granulomatosis (LyG) is a rare lymphoproliferative disorder associated with Epstein-Barr virus (EBV) in which there is an infection of B cells and numerous reactive T cells. The lymphoproliferative disorder progresses to organ infiltration and resultant dysfunction of affected organs. Histologically, it is characterized by a triad of polymorphic lymphoid infiltrate, angiitis, and granulomatosis. The lungs are the most commonly involved sites for lymphomatoid granulomatosis, but other sites that can be involved include the liver, skin, and central nervous system. The signs and symptoms of LyG can vary, and can produce generalized symptoms such as cough, shortness of breath, and chest tightness, but can vary depending on the location of LyG. CASE REPORT We report a case of a 60-year-old man who presented with altered mental status. Cross-sectional imaging of the brain was negative for any acute intracranial process, but a fine-needle biopsy of a retroperitoneal lymph node revealed nodular polymorphous mononuclear infiltrates containing atypical large EBV-positive B cells with positive EBER and CD30, consistent with lymphomatoid granulomatosis. The patient was started on a regimen of brentuximab/bendamustine, and instructed to follow up with Oncology on an outpatient basis. CONCLUSIONS Treatment options for lymphomatoid granulomatosis are based on the disease grading. Lymphomatoid granulomatosis can be classified by using a grading system determined by the number of EBV-positive large B cell malignant cells, along with necrosis. The most effective treatment for lymphomatoid granulomatosis is unknown, but at this time treatment protocols are based on the grade of the disease. The clinical and histological features of lymphomatoid granulomatosis are discussed in this case report.