Pituitary blastoma.

A 13-month-old Korean female presented with Cushing disease and diabetes insipidus. On MRI, a 3.5-cm, focally cystic, contrast-enhancing, sellar and suprasellar mass was noted. Aside from blood adrenocorticotropin (ACTH) and cortisol elevation, other pituitary hormone blood levels were normal or markedly reduced. The subtotally resected lesion consisted of synaptophysin-immunoreactive lobules of (a) large, polygonal, amphophilic, PAS-positive cells immunoreactive for ACTH, beta-endorphin, alpha melanocyte stimulating hormone (MSH), and keratin (CAM5.2) in some cells showing Crooke hyaline change, (b) less frequent acidophilic, growth hormone (GH) immunoreactive cells, and (c) rare luteinizing hormone (LH) and/or alpha subunit immunopositive cells. Also conspicuous were smaller cells resembling Rathke-type epithelium forming rosettes to sizable glands immunoreactive for EMA, keratin, S-100 protein, galectin-3 and rarely for synaptophysin and/or one of the above-noted adenohypophysial hormones. Transcription factors, including Neuro-D1 and Pit-1, were present in ACTH- and GH-producing cells, respectively, but only in occasional Rathke-type cells. The MIB-1 labeling index (LI) was 1.5% in secretory cells and 39% in Rathke-type epithelium. Ultrastructurally, the tissue resembled fetal pituitary of 10-12 weeks gestation and contained fully differentiated corticotrophs and somatotrophs, scant cells of glycoprotein-hormone producing type with small secretory granules, and glandular epithelial cells consistent with committed, but largely undifferentiated Rathke-type epithelium. We consider the tumor as a pituitary blastoma, a lesion composed of multiple cell types common to the development of the affected organ based upon (a) prominence of primitive Rathke-type epithelium, (b) disposition of secretory cells in lobules rather than acini, (c) the limited range of secretory cells represented, (d) the presence of their corresponding transcription factors, and (e) ultrastructural features indicating orderly development of the 10- to 12-week embryonic stage.

MR imaging findings of Rathke's cleft cysts: significance of intracystic nodules.

BACKGROUND AND PURPOSE: Rathke's cleft cysts often may be difficult to differentiate from other intrasellar or suprasellar masses on radiologic studies. The purpose of this study was to describe the significance of intracystic nodules, a diagnostic characteristic found in Rathke's cleft cysts, on MR images. METHODS: A retrospective review of MR studies was conducted for 13 patients who, after pathologic analysis, were diagnosed as having Rathke's cleft cyst. These patients underwent unenhanced and contrast-enhanced T1- and T2-weighted axial and coronal spin-echo sequential imaging. The signal intensity and incidence of the intracystic nodules on T1- and T2-weighted images were analyzed. The signal intensity of the nodule was compared with that of white matter and surrounding cyst fluid. The signal intensity of cyst fluid was compared with the intraoperative appearance of the cyst fluid. Biochemical and pathologic analyses of the intracystic nodules were conducted in two cases. RESULTS: An intracystic nodule having high signal intensity on T1-weighted images and low signal intensity on T2-weighted images was observed in 10 (77%) of the cases. At surgery, intracystic nodules were yellow, waxy, solid masses. Pathologic analysis showed this nodule to be a mucin clump. Biochemical analysis of the intracystic nodules showed cholesterol and proteins as the main constituents. In the Rathke's cleft cyst with intracystic nodules, cyst fluid revealed low signal intensity to isointensity relative to the intensity of the nodules on T1-weighted images, and isointensity to high signal intensity on T2-weighted images. Intracystic nodules were clearly visible on T2-weighted images. CONCLUSION: Because cyst fluid of Rathke's cleft cysts shows variable intensities on MR images, the specific diagnosis is often difficult when based on MR signal intensity values alone. The presence of an intracystic nodule with characteristic signal intensities on MR images may be indicative of the diagnosis of Rathke's cleft cyst.