Regression of Diffuse B‐cell Lymphoma of the Leg with Intralesional Gentian Violet

In this case report, a patient of primary cutaneous diffuse B-cell lymphoma, leg type was treated with intralesional gentian violet as she was judged to be too medically fragile for conventional chemotherapy due to advanced age and multiple serious comorbidities. Gentian violet (crystal violet/hexamethyl pararosaniline) is a triphenylmethane dye. It has been shown to have an inhibitory effect on NADPH oxidase, an enzyme family which is found in abundance in reactive oxygen-driven tumors such as melanoma and lymphoma. We hypothesize that intralesional gentian violet treatment caused signalling changes in the lymphoma which allowed for immune clearance of the lymphoma. Complete resolution of the patient's lesion was noted on a follow-up visit.