Anorectal malignant melanoma: preoperative usefulness of magnetic resonance imaging.

Magnetic resonance imaging (MRI) findings in three patients with primary anorectal malignant melanoma are described. Two patients had melanotic and one had amelanotic anorectal melanoma. The findings of MRI with a pelvic coil and an endorectal coil were consistent with pathologic findings. MRI with a pelvic coil demonstrated the melanotic component as high signal intensity on T1-weighted imaging. MRI with a pelvic coil and an endorectal coil was useful for staging anorectal melanoma. This article describes the initial report of the use of an endorectal coil for malignant melanoma of the anorectum.