Hairy cell leukemia involving an inguinal hernial sac

A 37-year-old man with hairy cell leukemia was found incidentally to have a right inguinal hernia. Microscopic examination of the resected herniorrhaphy specimen disclosed dense transmural infiltration by hairy cells. Electron-microscopic and immunoperoxidase studies confirmed the presence of surface cytoplasmic projections and B cell phenotype, respectively, of the infiltrating cells. This case is, to our knowledge, the first reported instance of hairy cell leukemia involving a hernial sac and demonstrates the capacity of hairy cells to infiltrate unexpected soft-tissue sites.