Primary sellar melanoma simulating hemorrhagic pituitary adenoma: MR and pathologic findings.

Primary intracranial melanoma is uncommon, and primary malignant melanoma of the sella turcica is exceedingly rare. We describe a 35-year-old woman who presented with endocrine dysfunction and CT findings suggestive of a prolactinsecreting macroadenoma. Subsequent MR findings revealed homogeneously short T1 and T2 relaxation times, yielding uniformly bright signal on T1 -weighted images and dark signal on T2-weighted images. At high field strength (1 .5 T), these characteristics seemed to implicate either paramagnetic effects suggestive of subacute hemorrhage or the intrinsically short relaxation times of lipidlike or mucinous material that may accumulate in a dermoid or Rathke cleft cyst. Following surgery, a final pathologic review revealed deeply pigmented, nonhemorrhagic malignant melanoma. The paramagnetic effect of stable free radicles of melanin is thought to account for the confusing MR characteristics of this uncommon lesion encountered at an unusual location [1-3).