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 en­ docrine dysfunction and CT findings suggestive of a prolactin­ secreting 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 ef­ fects 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 ef­ fect 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). Case Report A 35-year-old woman presented with a 3-year history of oligomen­ orrhea, intermittent galactorrhea, and headache. Her prolactin level was 102.5 ngjml (normal range, 0-20 ngjml). Contrast-enhanced CT revealed a homogeneously hyperden se lesion in the sella turcica with suprasellar extension. High-field-strength MR (G E 1.5 T) confirmed the presence of a pituitary mass, demonstrating very high signal intensity on T1-weighted images, and low sig nal intensity on T2weighted images (Fig. 1 ). The CT and MR appearance of the mass suggested a histologically complex lesion harboring a paramagnetic substance. The combination of clini cal findings, laboratory-docu­ mented hormonal derangements, and imaging results prompted con­ sideration of hemorrhagic pituitary adenoma (the favored preoperative diagnosis) or a developmental inclusion tumor of dermal origin . At transphenoidal hypophysectomy, a firm , dark black/purple mass was exposed and a biopsy was done. Frozen section specimens were interpreted as showing no evidence of tumor. Initially , the lesion was thought to represent an area of old hemorrhage with hemosiderin deposition. However, permanent histologic sections demonstrated a markedly pleomorphic tumor. Large amounts of melanin pigment were identified on both Fontana and melanin bleach stains . Prussian blue stain s were negati ve for iron (Fig. 2) . These distinctive histologic findings confirmed the final pathologic diagnosis as malignant mela­ noma. Postoperatively, ophthalmoscopic, gynecologic, and dermatologic examinations were negative. Endoscopy of the gastrointestinal tract also failed to reveal an extracranial primary tumor. Complete hypo­ physectomy, followed by moderate-dose radiotherapy was recom­ mended, but the patient refused further treatment. MR of the sella 3 months later showed regrowth of the tumor, filling the entire sella turcica and adjacent suprasellar cistern . Hyperintensity was again noted on T1-weighted images and hypointensity was seen on T2weighted images.