KRT5 and lymphoma: However, in limited biopsies, or those with intense inflammation, additional immunohistochemical (IHC) markers such as pan-cytokeratin (CKAE1/AE3), CK5/6, and LMP1 are often employed to aid in distinguishing NK-NPC from benign lymphoid proliferations, lymphomas, or poorly differentiated non-nasopharyngeal carcinomas.