MRI spectroscopy allows for spectroscopic evaluation of a specific soft-tissue area. Another technique to identify occult metastases is labeling lymph nodes with a marker. Isosulfan blue has been an effective substance in identifying sentinel nodes in patients with melanoma, but attempts to use it in the head and neck in patients with squamous cell carcinoma have been disappointing. Photosensitizing drugs used in photodynamic therapy have potential use for labeling occult metastases. These drugs remain in the tumor cells longer than in normal tissue and fluoresce under black light.
Studies currently are underway to assess the diagnostic applications of photodynamic therapy.
In patients undergoing prophylactic neck dissection, the fatty lymphatic tissue is examined with a black light, and areas that fluoresce are sent for pathologic examination to determine if this area contains squamous cell carcinoma. Imaging of nodal metastases in the head and neck. The extracapsular spread of tumors in cervical node metastasis. Predictive value of tumor thickness in squamous carcinoma confined to the tongue and floor of the mouth. Medicine is a constantly changing science and not all therapies are clearly established.