An 83-year-old man was diagnosed with hairy cell leukemia (HCL). He was treated with cladribine and achieved partial remission. However, pancytopenia due to HCL bone marrow involvement progressed slowly. Nine years later, he developed rectal cancer. Prior to the surgery, endoscopy-assisted submucosal ink injection was performed to identify the area of lower intestinal lesions. The following day, he developed septic peritonitis with shock status, perhaps due to his neutropenia and ink injection procedures. Surgical resection of the cancer was presumed unfeasible; therefore, radiation was performed. Several months later, bone marrow examination revealed HCL infiltration with reticulin fibrosis. Chemotherapy regimens with purine nucleoside analogs, which are the standard treatments for HCL, might accentuate the progression of his rectal cancer and enhance the development of severe infections. Therefore, interferon (IFN) -α was administered as an alternative therapy. Three months later, pancytopenia resolved, and bone marrow examination revealed a remarkable improvement in HCL infiltration and marrow fibrosis. With IFN-α therapy, the patient successfully underwent surgical resection of the rectal cancer. Using INF-α, a prompt recovery from pancytopenia might be expected even in a patient with advanced HCL, who requires surgical treatment for a concomitant cancer.
Keywords: Hairy cell leukemia; Interferon; Second malignancy.