[MR imaging of mucocutaneous malignant melanoma in the head and neck]

MR imaging was performed in three patients with mucocutaneous malignant melanoma of the head and neck, and surgical specimens were investigated in MR-pathological correlation. Two of 3 cases were revealed to be melanotic melanoma; one arose in the maxillary sinus, and another in the bulbar conjunctiva. The remaining case was amelanotic melanoma originating in the nasal cavity. Two cases of melanotic melanoma showed different intensity on T1WI according to the melanin concentration; the more the melanin-producing process existed, the higher intensity in the tumor was shown. On T2WI there were also some differences in signal intensity; the case having more concentration of melanin changed lower partially in the areas where very high intensity was noted on T1WI, while another case remained unchanged. These findings are based on the inherent paramagnetic effect mostly compatible with the previous reports. On the other hand, the amelanotic melanoma was demonstrated as an intermediate intensity both on T1- and T2WI. Because of the higher incidence of hemorrhage in/around the tumor, it is an important diagnostic clue to this tumor, as in our case of amelanotic type. On reviewing the three cases, we consider that MR imaging offers a useful adjunct in the diagnosis of malignant melanoma.