Medullary carcinoma of the thyroid requires aggressive treatment because of its potential to metastasize and because of the current limitations of preoperative localization and systemic therapy. If these tumors could be made to fluoresce in vivo with tagged fluorophore antibodies against tumor antigens, surgeons would be able obtain additional information in the operating room to facilitate a more complete resection. Based on the success of our previous work in breast and colon cancer models, we conducted an animal study of in vivo tumor fluorescence of a human medullary thyroid cell line in which bright tumor fluorescence is visible during dissection. To accomplish this, we used an inexpensive and commercially available handheld, blue (470 nm), light-emitting diode flashlight and filtered goggles (520 nm). This procedure, which we call the fluorescent antibody-assisted surgical technique (FAAST), is easy to perform, requires no complex or expensive technical equipment, and has the potential to be applied to a wide variety of tumors. To the best of our knowledge, this is the first experiment of its kind to be reported in the literature.