Lasers in the visible light region are absorbed more in pigmented than in nonpigmented tissues. Therefore, various pigments have been used for nonpigmented malignant tumors for more effective laser treatment. Suspensions of iron particles, ferrofluids, have been investigated not only as colorants of tissue but also for the added effects of movement by magnetic fields and the possibility of induced heat in tissues by microwaves. A preliminary study has been done of ferrofluids injected in a nonpigmented basal cell epithelioma of a patient with multiple basal cell epitheliomas. The patient has been observed for more than three years.
Goldman L, Johnson J. Laser Treatment of Basal Cell Epithelioma Injected With Magnetic Iron Particles. Arch Dermatol. 1974;110(5):751-752. doi:10.1001/archderm.1974.01630110045010