Epstein-Barr Virus (EBV)-Positive Diffuse Large B-Cell Lymphoma in a Young Patient: A Difficult Diagnosis.

Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma (EBV+DLBCL) was initially hypothesized to occur against a background of age-related immunodeficiency and was classified as EBV-positive DLBCL of the elderly. Subsequent reports of younger patients led to the renaming of the disease. A 17-year-old girl with no significant medical history presented with a left neck mass. Positron emission tomography-CT revealed augmented FDG accumulation in the left neck and multiple FDG accumulations in other lymph nodes, necessitating a biopsy. Histological findings revealed destruction of the follicular structure within the lymph nodes, with some parts exhibiting nodular formation due to fibrosis. Large Hodgkin/Reed-Sternberg (HRS)-like cells intermingled with small lymphocytes and histiocytes were observed. Immunostaining revealed that the HRS-like cells were positive for CD20 and EBER-ISH and negative for CD30 and CD15. The expression of PD-L1 was observed in tumor cells, whereas the cells were mostly negative for c-Myc. The patient was young and exhibited no symptoms indicative of immunodeficiency, thereby supporting the hypothesis of a pathogenesis derived from immune evasion. We focused on the relationship between PD-L1, which is involved in immune evasion mechanisms, and c-Myc, which may directly contribute to the immune escape of tumor B cells.