[Oligomelanotic malignant melanoma in the nasal cavity diagnosed by IMP scintigraphy]

MRI, 67Ga scintigraphy, and 123I-IMP-SPECT were performed in the patient with oligomelanotic malignant melanoma in the nasal cavity which is not confirmed pathologically at first. MRI failed to diagnose the tumor as malignant melanoma. It was difficult to differentiate malignant melanoma from malignant lymphoma in 67Ga scintigraphy. The remarkable accumulation of 123I-IMP was consistent with the tumor localization in the nasal cavity. This tumor uptake was thought to be oligomelanotic or amelanotic melanoma since the accumulation was more distinctive at the delayed image and since the tumor was not visibly melanotic. Finally the tumor was confirmed to be oligomelanotic melanoma by immunohistochemical examination; which was in accordance with IMP-SPECT findings. Oligomelanotic or amelanotic melanoma occurs in nasal cavity with high frequency. We report here the oligomelanotic melanoma case where IMP-SPECT was rather useful to make a pathological diagnosis than other imaging modalities.